calcitonin and Hypocalcemia

Possible local and systemic adverse effects following administration of salmon (sCT) and human (hCT) calcitonin (CT) have been evaluated in a double-blind, within-subject, comparative trial in 30 young, healthy volunteers. Each subject received 0.25 and 0.5 mg hCT and 100 IU sCT s.c.. Adverse effects and hypocalcaemia were recorded 1, 3 and 6 h after each injection. Significantly fewer local adverse reactions were observed after hCT (20 or 33%) than after sCT (80%), possibly due to the different vehicles employed (mannitol solution and acetic acid). The most frequent systemic adverse effects were gastrointestinal (nausea, vomiting), which occurred in 80% after 1 h, independently of the CT--preparation used. Hypocalcaemic changes were generally small and lasted longer after sCT. It is concluded that the hCT preparations were better tolerated locally than sCT in young, healthy volunteers, and that there were no differences in the systemic side effects or hypocalcaemic activity.

Topics: Adult; Animals; Calcitonin; Double-Blind Method; Female; Gastrointestinal Diseases; Humans; Hypocalcemia; Injections, Subcutaneous; Male; Skin Diseases

Salmon calcitonin (sCT) is a potent calcium-regulating peptide hormone and widely applied for the treatment of some bone diseases clinically. However, the therapeutic usefulness of sCT is hindered by the frequent injection required, owing to its short plasma half-life and therapeutic need for a high dose. Oral delivery is a popular modality of administration for patients because of its convenience to self-administration and high patient compliance, while orally administered sCT remains a great challenge currently due to the existence of multiple barriers in the gastrointestinal (GI) tract. Here, we introduced an orally targeted delivery system to increase the transport of sCT across the intestine through both the paracellular permeation route and the bile acid pathway. In this system, sCT-based glycol chitosan-taurocholic acid conjugate (GC-T)/dextran sulfate (DS) ternary nanocomplexes (NC-T) were produced by a flash nanocomplexation (FNC) process in a kinetically controlled mode. The optimized NC-T exhibited well-controlled properties with a uniform and sub-60 nm hydrodynamic diameter, high batch-to-batch reproducibility, good physical or chemical stability, as well as sustained drug release behaviors. The studies revealed that NC-T could effectively improve the intestinal uptake and permeability, owing to its surface functionalization with the taurocholic acid ligand. In the rat model, orally administered NC-T showed an obvious hypocalcemia effect and a relative oral bioavailability of 10.9%. An in vivo assay also demonstrated that NC-T induced no observable side effect after long-term oral administration. As a result, the orally targeted nanocomplex might be a promising candidate for improving the oral transport of therapeutic peptides.

Topics: Administration, Oral; Animals; Biological Availability; Biological Transport; Caco-2 Cells; Calcitonin; Calcium; Calcium-Regulating Hormones and Agents; Chitosan; Dextran Sulfate; Drug Delivery Systems; Drug Liberation; Drug Stability; Half-Life; Humans; Hypocalcemia; Injections, Subcutaneous; Intestinal Absorption; Male; Nanocomposites; Rats; Rats, Sprague-Dawley; Taurocholic Acid

The aim of this study was to investigate two types of chitosan-modified poly (DL-lactic-co-glycolic acid) (PLGA) nanocomposite particles containing salmon calcitonin for pulmonary delivery, which were obtained using spray drying fluidized bed granulation (Agglomaster™) and dry powder coating techniques (Mechanofusion™), respectively. The physicochemical properties, pulmonary distribution, pulmonary clearance rate as well as in vivo hypocalcemia actions of the two types of nanocomposite particles were investigated. As indicated by scanning electron micrographs, soft matrix nanocomposite particles and soft ordered nanocomposite particles were produced by Agglomaster™ and Mechanofusion™, respectively. Both forms of chitosan-modified PLGA nanocomposite particles exhibited a high inhalation efficiency, i.e. more than 50% of the two types of nanocomposite particles could be deposited in the deep lung of male Wistar rats. However, the chitosan-modified PLGA nanocomposite particles designed by Agglomaster™ exhibited superior properties to those obtained by Mechanofusion™ with respect to the redispersibility of fine particles in aqueous liquid, the pulmonary retention time and pharmacological effects. In addition, compared with non-modified PLGA nanocomposite particles, the chitosan-modified PLGA nanocomposite particles obtained by Agglomaster™ exhibited enhanced pulmonary absorption of salmon calcitonin via the lung. The findings in this study suggest that the spray drying fluidized bed granulation technique is superior to the dry powder coating technique for producing chitosan-modified dry powder formulations containing salmon calcitonin for inhalation. This can be attributed to the avoidance of aggregation of chitosan-modified PLGA nanocomposite particles when using Agglomaster™ rather than Mechanofusion™.

Topics: Absorption; Administration, Inhalation; Animals; Calcitonin; Chemistry, Pharmaceutical; Chitosan; Hypocalcemia; Lactic Acid; Lung; Male; Nanocomposites; Nanoparticles; Particle Size; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Powders; Rats; Rats, Wistar; Technology, Pharmaceutical

Even though salmon calcitonin (sCT) has been known as a potent hypocalcemic agent, only injection or nasal spray products are available on the market. In order to develop oral delivery system of the agent, a novel sCT-sodium tripolyphosphate (STPP) ionic complex was fabricated and also characterized. For the optimization of the ionic complexation, the effect of incubation time and molar ratio between sCT and STPP was evaluated. Particle size of the ionic complex in aqueous media, SEM images, DSC, FT-IR, in vitro release test, stability within the simulated intestinal fluid, and hypocalcemic effect were evaluated. The optimal molar complexation ratio of sCT to STPP was ranged from 1:5 to 1:10 and the complexation efficiency was about 95%. The SEM image has shown that the freeze dried ionic complex has rough morphology in their surface and the particle size in PBS (pH 7.4) was about 220nm. The DSC and FT-IR results provided evidences for ionic interaction between -NH(2) groups and -P horizontal lineO groups of sCT and STPP, respectively. The sCT ionic complex has shown sustained sCT releasing characteristics for 3weeks. The sCT-STPP ionic complex was protective to enzymatic attack and in vivo animal data revealed that the present ionic complex would show continuous hypocalcemic effect. Conclusively, the present sCT-STPP ionic complex formulation thought to be a novel oral delivery candidate for the treatment of osteoporosis.

Topics: Administration, Oral; Animals; Calcitonin; Calorimetry, Differential Scanning; Drug Stability; Hypocalcemia; Ions; Male; Particle Size; Polyphosphates; Rats; Rats, Sprague-Dawley; Spectroscopy, Fourier Transform Infrared

We have previously described the design and synthesis of Mal-sCT and compared its biological activity with its reversible counterpart, REAL-sCT. Mal-sCT was salmon calcitonin (sCT) conjugated with two molecules of an epsilon-maleimido lysine derivative of palmitic acid via non-reversible thioether bonds at its cysteine residues while REAL-sCT was sCT conjugated with two molecules of a cysteine derivative of palmitic acid via reducible disulfide bonds at its cysteine residues. Neither compounds when dissolved in water could reproducibly improved the oral deliverability of sCT. The purpose of this study was to characterize and evaluate Lipeo-sCT, a novel sCT analog conjugated via reducible disulfide bonds with two amphiphilic groups consisting of a hydrophobic hexadecyl moiety attached via an ether bond to a hydrophilic triethylene glycol moiety. Lipeo-sCT was successfully synthesized by a 4-step reaction, purified and identified by ESI-MS. Analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM) suggested it had a propensity to form aggregates in water, although the aggregation behavior was controllable by modulating solvent polarity. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay indicated a lack of cytotoxicity against the Caco-2 cells at up to 100 microM. Compared with sCT, Lipeo-sCT lowered plasma calcium to comparable levels when injected subcutaneously at 0.15 mg/kg into female Wistar rats, but the hypocalcemic activity of Lipeo-sCT was prolonged by at least 6 more hours. This was attributable to a continual regeneration of sCT from Lipeo-sCT. sCT was detectable in plasma 8h following subcutaneous injection of Lipeo-sCT (1.90 mg/kg), while Lipeo-sCT was not observed in plasma at all time points. By comparison, sCT was detectable in plasma for less than 2.5h following subcutaneous injection at an equivalent dose (1.50mg/kg). Data from this study complement those of previous studies, and add to the body of knowledge correlating the in vivo activity of lipidized peptides to their physical properties.

Topics: Animals; Biophysics; Caco-2 Cells; Calcitonin; Chromatography, High Pressure Liquid; Female; Humans; Hypocalcemia; Lipids; Magnetic Resonance Spectroscopy; Microscopy, Electron, Transmission; Particle Size; Rats; Rats, Wistar

The ovariectomized rat has proved to be a most useful model for preclinical testing of potential therapies for osteoporosis. We describe the immediate effects of a single treatment with salmon calcitonin (sCT) on calcium homeostasis and bone turnover markers in 6-month-old sham and ovariectomized (ovx) rats at 15 days postovariectomy. Rats were fasted for 24 h prior to and following administration of 0.3 microg/kg body weight sCT. Blood specimens were collected at 0 (pretreatment), 2, 4, and 8 h. Urine samples were collected during the intervening periods. sCT treatment produced a decrease in blood ionized calcium at 2 h posttreatment in sham and ovx rats (P < 0.001), which was exaggerated in the ovx rats (P < 0.001). Increased parathyroid hormone (PTH) levels (P < 0.001) accompanied the hypocalcemia in ovx rats. Furthermore, PTH levels were significantly higher in ovx rats compared with sham rats for the same ionized calcium range of 1.275-1.300 mmol/l (P < 0.05). sCT treatment in sham rats increased urine hydroxyproline (UHyp) at 6 h posttreatment (P < 0.01). In conclusion, the calcitonin-induced hypocalcemia and secondary hyperparathyroidism was more pronounced in the ovariectomized rats, consistent with the actions of calcitonin in states of increased bone turnover induced by estrogen deficiency. This study highlights the importance of considering the actions of PTH and estrogen status when interpreting changes in calcium homeostasis and bone turnover following treatment with calcitonin in rodent models and provides further evidence for a potential role of estrogen in parathyroid function.

Topics: Animals; Body Weight; Bone and Bones; Calcitonin; Calcium; Estrogens; Female; Homeostasis; Hydroxyproline; Hypocalcemia; Ovariectomy; Parathyroid Hormone; Rats; Rats, Sprague-Dawley; Time Factors

In the in vitro experiment using a luminal, mucosal, and fecal fluid/extract from jejunum and colon of a rat, Lys18-residue modified mono-PEG(2k)-sCT (Lys18-PEG(2K)-sCT) exhibited a longer half-life than salmon calcitonin (sCT) in a colonic fluid and its extract. A physical adsorption study showed that Lys18-PEG(2K)-sCT had lower adsorption in the feces than sCT over an 8-hr period. An absorption study of the sCT and Lys18-PEG(2K)-sCT from the jejunum and colon using an in situ closed-loop technique in anesthetized rats showed a dose-dependent reduction in the plasma Ca2+ level but to a certain limit. Furthermore, the hypocalcemic response by intracolonic administration was significantly higher than the intrajejunal one, demonstrating that the colon had better absorption. In particular, Lys18-PEG(2K)-sCT (5 microg/rats) produced the most pronounced hypocalcemia after the intracolonic administration, which resulted in a sustained reduction in the serum calcium level over an 8-hr period, with a maximum reduction (% max(d)) of 38% after 4 hr. The overall reduction in the serum calcium levels, which was expressed as the net change in the AUC relative to the control over an 8-hr period, was 25.51 +/- 3.38 for Lys18-PEG(2K)-sCT. The relative pharmacological bioavailability of the intracolonically administered Lys18-PEG(2K)-sCT was 2.1-fold higher than sCT and the absolute pharmacological bioavailability was 73.59% of i.v.-injected sCT in an 8-hr period. Overall, this study highlights the feasibility of the oral delivery of Lys18-PEG(2K)-sCT in achieving a sustained calcium-lowering effect.

Topics: Administration, Oral; Adsorption; Animals; Calcitonin; Colon; Drug Stability; Hypocalcemia; Intestinal Absorption; Male; Polyethylene Glycols; Rats; Rats, Sprague-Dawley

The conformational and lipid binding properties of several calcitonin analogs were compared. These analogs were designed to have the central amphipathic helical region of salmon calcitonin and N- and C-terminal segments similar to human calcitonin. The various analogs differed from one another either by removal of Leu19 from this hybrid analog, replacement of Leu19 with Gly19 or having a carboxyl terminus more closely related to salmon calcitonin. It had been found that replacement of Leu19 with Gly19 caused a marked reduction in the hypocalemic activity of the analog. The ability of the analogs to form helical structures in the presence of dimyristoylphosphatidylglycerol as well as their ability to lower the enthalpy of the calorimetric phase transition of this phospholipid correlates well with the hypocalcemic potency of the peptide.

Topics: Amino Acid Sequence; Animals; Calcitonin; Humans; Hypocalcemia; Models, Molecular; Molecular Sequence Data; Phosphatidylglycerols; Protein Conformation; Thermodynamics

To evaluate the hypocalcemic effect of polyethylene gtycol-conjugated salmon calcitonins (PEG-sCT) in rats, mono-PEGylated sCTs (mono-PEG-sCTs) and unmodified sCT were administered via the intranasal route and serum calcium levels were measured by colorimetric assay using o-cresolphthalein. Mono-PEG-sCTs were prepared with different sizes of succinimidyl succinate monomethoxy PEG molecules (PEG2K), PEG5K, PEG12K) and characterized by HPLC and MALDI-TOF mass spectrometry. Nasal instillation of mono-PEG2K-sCT at a dose of 2 IU/kg resulted in sustained reduction in serum calcium levels over 8 hr, with a maximum reduction (% maxd) of 13% after 6 hr of application. Whereas unmodified sCT showed a transient decrease in serum calcium levels with the maximum reduction (5%) observed after 30 min of administration. The overall reductions in serum calcium levels expressed as the net change in AUC relative to control in 8 hr were 11.9 +/- 0.2, 4.6 +/- 0.7, and 2.6 +/- 0.7% for mono-PEG2K-, mono-PEG5K-, and mono-PEG12K-sCT, respectively, compared to 3.2 +/- 0.6% for unmodified sCT. The relative bioavailability of nasally administered 2 IU/kg of mono-PEG2K-sCT was approximately 4-fold higher than nasally administrated unmodified sCT, and the absolute bioavailability was approximately 91% of intravenously injected sCT in 8 hr. It can be concluded that the intranasal absorption of mono-PEG-sCTs was inversely related to the molecular weights of the PEG attached. Of the PEGylated sCTs examined, mono-PEG2K-sCT showed the most pronounced hypocalcemic effect. Therefore the intranasal application would probably be an alternative route of administration for mono-PEG-sCTs in achieving sustained calcium-lowering effects.

Topics: Administration, Intranasal; Animals; Area Under Curve; Biological Availability; Calcitonin; Calcium; Chromatography, High Pressure Liquid; Hypocalcemia; Male; Molecular Weight; Polyethylene Glycols; Rats; Rats, Sprague-Dawley; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization

Salmon calcitonin (sCT) was prepared in good yield and high purity by the condensation of Nalpha-Boc-cyclic decapeptide, Boc-C1SNLSTC7VLG-OH (1,7-disulfide), with protected docosapeptide (Psc)LSQE(OPse)LHK(Psc)LQTYPRTNTGSGTP-NH2 x 3TFA, followed by deprotection of Boc with trifluoroacetic acid and Psc/Pse with piperidine. The 2-(phenylsulfonyl)ethoxycarbonyl (Psc) and 2-(phenylsulfonyl)ethyl (Pse) protecting groups were recently developed. The two peptides were built up by stepwise and fragment condensation using appropriate Nalpha-Boc-amino acids and subsequent deprotection in solution. The synthetic sCT exhibited hypocalcemic potency of more than 4000 IU/mg in rats.

Topics: Amino Acid Sequence; Animals; Calcitonin; Formic Acid Esters; Hypocalcemia; Molecular Sequence Data; Rats

Salmon calcitonin (5 micrograms/kg body wt) was administered in an elasmobranch, Dasyatis akajei, to investigate the effects upon plasma calcium and inorganic phosphate. The hormone produced hypocalcemia and hyperphosphatemia in the stingray. It is concluded that calcitonin may have a role in calcium homeostasis by a mechanism different from that on bones.

Topics: Animals; Calcitonin; Calcium; Cohort Studies; Elasmobranchii; Female; Homeostasis; Hypocalcemia; Injections, Intraperitoneal; Male; Phosphates; Salmon; Time Factors

Serum calcium levels were markedly reduced in male freshwater catfish Heteropneustes fossilis following hypophysectomy. The administration of salmon calcitonin to intact fish had no effect on serum calcium level, whereas the same treatment to hypophysectomized fish induced hypocalcemia.

Topics: Animals; Calcitonin; Calcium; Catfishes; Hypocalcemia; Hypophysectomy; Male; Pituitary Gland

The experimental and clinical effectiveness of nasal salmon calcitonin (SCT) for treatment of osteoporosis in humans has been well established, but none is known yet about the pharmacokinetic property in relation to therapeutic efficacy, especially when used in a therapeutic dose range. This preclinical study was designed to evaluate such a property, first of all in rats, using a novel heterogeneous two-site enzyme immunoassay that has allowed us to evaluate the pharmacokinetic property of parenteral SCT in rats due to the high sensitivity (the detection limit = 2 pg of SCT/ml of plasma). It was found that as early as 10 min after the nasal dosing of 1.25, 5, or 20 U/rat, the SCT immunoactivity became detectable in plasma and thereafter it waned rapidly with time. Hypocalcemia developed in a dose-dependent manner, but with a delay of approximately 20 min from the peak of the immunoactivity and lasted hours. The pharmacokinetic parameters measured for the doses (1.25, 5, and 20 U/rat) were as follows; the AUCs (pg.hr/ml) = 20.8, 89.0, and 189, and the MRTs (min) = 52, 54, and 45, respectively. The results appear to suggest: (1) the unexpected quick transfer of nasal SCT into and from the circulation, (2) a delayed onset of hypocalcemia and possibly its anti-osteopenic action, both of which may last longer, (3) that keeping the plasma SCT above the in vitro anti-osteoclastic level (approximately 1 pM) only for a few hours per 2 days would be enough for inducing the distinct anti-osteopenic effect in rats, and (4) the feasibility of designing the clinical study as to the pharmacokinetics and pharmacodynamics of nasal SCT on humans.

Topics: Administration, Intranasal; Analgesics; Animals; Area Under Curve; Biological Availability; Bone Diseases, Metabolic; Calcitonin; Hypocalcemia; Immunoassay; Male; Rats; Rats, Wistar

The activity of a novel calcitonin SB 205614 was compared with salmon calcitonin (sCT) and (Asu1,7)-eel calcitonin (ELC) in six different models of osteoclastic bone resorption in vitro and in vivo. SB 205614 is an ELC analogue that has an acetylenic bridge instead of the natural disulphide bridge, rendering the molecule more stable biologically than sCT and equally stable to ELC. Our aim was to determine whether this structural change compromised biologic activity, and if not, whether the increased stability could be used to exploit novel modes of administration. In the in vitro assays of pit formation by disaggregated rat osteoclasts on cortical bone slices (DROcA) and PTH stimulation of 45Ca-release from prelabeled fetal rat bone, no significant differences in activity were observed between the three calcitonins. In the DROcA, IC50s of 0.003, 0.015 and 0.064 pg/ml for sCT, ELC, and SB 205614, respectively, were determined, with total or near complete inhibition observed at 1 pg/ml (0.3 pM). In the assay of PTH-stimulation of 45Ca release, IC50s were measured of 5.5, 4.8, and 12.9 pM for sCT, ELC, and SB 205614, respectively; in every case maximal inhibition (ca. 80%) was observed at 30 and 100 pM. The internationally approved U.S. Pharmacopoeia bioassay of hypocalcemia in the rat following intravenous (IV) administration indicated that SB 205614 had a greater potency than ELC or sCT. More important, a full dose-hypocalcemic response curve demonstrated significantly increased potency compared to sCT or ELC, as the doses causing 15% lowering of serum calcium (approximately 50% of the maximum effect) were 33.9, 25.2, and 12.9 mg/kg for sCT, ELC, and SB 205614, respectively. As a preliminary means of investigating alternative delivery forms of calcitonin, the time course of the hypocalcemic effect was investigated in the rat and rabbit following IV administration, and was compared with that following intranasal (IN) administration (rat and rabbit), and following intracolonic administration (rat only). Maximal effects were similar, whereas in general the hypocalcemic effect of SB 205614 was of a longer duration than the other two calcitonins; this was reflected in a larger area over the curve (AOC). However, following IN administration in the rabbit, where an aerosol delivery device similar to that used in the clinic was used to administer the calcitonins, SB 205614 (100 IU/kg) induced a highly significant two-fold increase in the AOC compared to ELC or sCT

Topics: Amino Acid Sequence; Animals; Bone Resorption; Calcitonin; Disease Models, Animal; Drug Administration Routes; Evaluation Studies as Topic; Hypocalcemia; In Vitro Techniques; Male; Molecular Sequence Data; Osteoclasts; Osteoporosis; Rabbits; Rats; Rats, Sprague-Dawley; Rats, Wistar

The work was performed to obtain a better understanding why the oral administration of calcitonin (CT)-loaded liposomes to rats results in a hypocalcemia, while liposomes are normally disrupted in the gastro-intestinal tract and cannot protect the hormone from enzymatic digestion.. In vitro comparisons between the stability of calcein and CT-loaded liposomes in the presence of cholate solutions led to an interpretation of the results observed. By means of gel filtration, turbidimetry, and fluorescence measurements, the interactions between CT and lipids were studied after sonicated liposomes had been broken down by cholate.. Experiments showed that CT in the external medium of a liposome suspension had no effect on the vesicles. Gel filtration of cholate-treated liposomes loaded with calcein and CT resulted in a total separation of calcein from the lipid fraction for detergent concentrations higher than 4 mM. However, 50% of the CT was reencapsulated even when the cholate-to-phospholipid molar ratio was increased up to 100. Incubation of cholate-solubilized liposomes with 1% trypsin resulted in a partial CT-breakdown.. These results strongly suggest that during membrane solubilization by cholate, lipid-CT complexes are formed which retain most of the CT initially embedded in the liposomal membrane, and which offer some protection to CT under the action of trypsin. The existence of these complexes could be one of the reasons for the reported hypocalcemia in rats after oral administration of CT-loaded liposomes.

Topics: Animals; Calcitonin; Cholic Acid; Cholic Acids; Chromatography, Gel; Drug Carriers; Drug Stability; Hypocalcemia; In Vitro Techniques; Liposomes; Rats; Solutions; Spectrometry, Fluorescence; Technology, Pharmaceutical; Trypsin

The effect of the polypeptide salmon calcitonin (sCT) on serum calcium concentrations following intranasal and intravenous administration was studied in young rabbits. A small, hypocalcemic effect was observed after nasal administration of sCT without additives, indicating that the nasal sCT absorption was low. The absorption could be improved by addition of an absorption-enhancing adjuvant to the nasal preparation. The absorption, however, was still far from complete as was apparent from the much stronger effect of intravenously injected sCT. When a number of sCT doses were given during a 10-week period, the hypocalcemic effect per sCT dose in the young rabbits decreased after intravenous and, although less pronounced, after nasal administration. The decreased response to sCT is probably not related to the induction of neutralizing antibodies or desensitization of sCT receptors, but is more likely associated with the age-dependent level of bone activity.

Topics: Absorption; Administration, Intranasal; Aging; Animals; Antibodies; Calcitonin; Calcium; Enzyme-Linked Immunosorbent Assay; Female; Hypocalcemia; Injections, Intravenous; Rabbits

The effects of proteolytic enzyme inhibitors, aprotinin, soybean trypsin inhibitor and camostat mesilate as absorption enhancers on the transdermal iontophoretic delivery of salmon calcitonin (SCT) have been examined in rats. The dermal absorption of SCT was evaluated with hypocalcaemic effect. Application of SCT (12.5 int. units/rat) onto abdominal skin did not produce any hypocalcaemic effect. This produced a small hypocalcaemic effect with cationic iontophoresis (drug phase, anode; reference phase, cathode; high frequency pulses of 1 V at 10 kHz, 2h). Furthermore, camostat mesilate (1 mM) and aprotinin (10(6) int. units mL-1) enhanced the hypocalcaemic effects on the application of SCT with iontophoresis. These hypocalcaemic effects were highest with the pH 4.0 preparation compared with those of the pH 5.5, pH 7.0 and pH 8.0 preparations. However, soybean trypsin inhibitor did not change the hypocalcaemic effects. This was because the soybean trypsin inhibitor is a relatively high molecular weight peptide (mol. wt 8000) and an anion at used pH, and therefore was not absorbed through rat skins with cation iontophoresis.

Topics: Absorption; Administration, Cutaneous; Animals; Calcitonin; Hypocalcemia; Iontophoresis; Male; Protease Inhibitors; Rats; Rats, Inbred Strains

In order to evaluate the potential inhibition of the acute anti-osteoclastic activity of salmon calcitonin (SCT) by specific antibodies (Ab), we compared the SCT-induced hypocalcemic effect in young male rabbits with significant titers of high affinity Ab and in matched animals without Ab. Immunization of rabbits was performed by repetitive s.c. injections of SCT and Freund adjuvant. Ab were present in four-fifths of SCT-treated rabbits (Ab+). Their titer varied from 0.8 x 10(-9) to 30 x 10(-9) M/liter and their constant of affinity from 0.97 x 10(9) to 4.2 x 10(9) L/M. Intravenous injection of 1 IU/kg SCT to Ab+ rabbits induced a significant decrease (P less than 0.01) of ionized serum calcium (Ca2+) after 30 minutes (mean +/- SD: -9 +/- 0.6%) and until the 240th minute of the test (-16.7 +/- 4.7%), with a maximum after 120 minutes (-22.6 +/- 2%). This was not significantly different from the hypocalcemic effect measured after the same procedure performed in matched animals without Ab (Ab-): significant decrease in Ca2+ (P less than 0.01) after 30 minutes (-8.2 +/- 2.2%), maximal after 150 minutes (-23.2 +/- 4.9%), and lasting until 210 minutes (-14.5 +/- 3.7%). We conclude that, in the particular model of the male young rabbit, specific anti-SCT Ab do not block or reduce the acute anti-osteoclastic activity of SCT.

Topics: Animals; Antibodies; Antibody Specificity; Calcitonin; Calcium; Hypocalcemia; Male; Osteoclasts; Rabbits; Vaccination

A new analog of salmon calcitonin (N alpha-propionyl Di-Ala1,7,des-Leu19 sCT; RG-12851; here termed CTR), which lacks the ring structure of native calcitonin, was tested for biological activity in several in vitro and in vivo assay systems. The analog (CTR) and salmon calcitonin (sCT) stimulated kidney cell adenylate cyclase activity and inhibited bone resorption in organ cultures of fetal rat long bones with similar potencies and efficacies. Furthermore, CTR and sCT, at similar doses, induced comparable hypocalcemic responses in mice following sc injection or infusions. However, unlike sCT, CTR did not induce anorexia and weight loss in rats following sc injection. These data suggest that the ring structure of sCT may be important for the anorexigenic effect but is not required for effect on bone resorption or calcium homeostasis. Clinical studies appear warranted as, potentially, CTR might induce fewer side effects than does sCT.

Topics: Adenylyl Cyclases; Animals; Anorexia; Body Weight; Bone Resorption; Calcitonin; Cyclization; Eating; Feeding and Eating Disorders; Hypocalcemia; Kidney; Male; Mice; Mice, Inbred ICR; Organ Culture Techniques; Rats; Structure-Activity Relationship

Topics: Administration, Intranasal; Antibodies; Calcitonin; Female; Humans; Hypocalcemia; Male; Osteitis Deformans

Topics: Calcitonin; Calcium; Diagnosis, Differential; Edetic Acid; Humans; Hypercalcemia; Hyperparathyroidism; Hypocalcemia; Parathyroid Hormone; Reference Values

Calcitonin (CT), when administered peripherally, is a potent hypocalcemic agent. This peptide can also exert a variety of profound effects through brain receptors after central injection. We examined the capacity of CT to alter plasma calcium of freely moving conscious rats after intracerebroventricular (i.c.v.) injection. A dose-dependent decrease in plasma calcium was seen after administration of 25 ng, 250 ng or 2500 ng of salmon calcitonin (sCT). The extent and duration of hypocalcemia after central injection was equal to, or greater than, that seen after giving the same doses of peptide intravenously (i.v.). Calcitonin gene-related peptide (CGRP), when administered centrally at a 50-fold molar excess, produced only a transient decrease in plasma calcium. No increase in plasma levels of sCT could be detected by RIA after i.c.v. injection, although measurable levels were obtained by i.v. injection. Centrally administered sCT did not appear to produce hypocalcemia by enhancing the release of endogenous rat CT. In contrast to the rise in rat immunoreactive parathyroid hormone (PTH) seen after i.v. injection of sCT, no significant elevation occurred after central administration of the peptide despite induction of comparable levels of hypocalcemia. Consequently, reduced PTH release may contribute to the central hypocalcemic action of CT. The results indicate that peptides acting through the brain CT receptor may modulate peripheral blood calcium.

Topics: Animals; Brain; Calcitonin; Calcium; Dose-Response Relationship, Drug; Hypocalcemia; Injections, Intraventricular; Male; Parathyroid Hormone; Rats; Rats, Inbred Strains; Time Factors

Although it is well established that parathyroid hormone and phosphate are important regulators of 1,25-dihydroxyvitamin D [1,25(OH)2D] production, it remains unclear whether calcitonin affects vitamin D metabolism in vivo. Experiments were performed in the rat to determine the effect of chronic calcitonin infusion (0.2 U X h-1) on plasma levels of vitamin D metabolites and on calcium metabolism. Thyroparathyroidectomized animals fed a calcium-replete or calcium-free diet were studied for as long as 2 wk before they were killed. In control rats, a calcium-free diet alone for 12 d resulted in an increase in 1,25(OH)2D levels from 24 +/- 5 to 139 +/- 37 pg . ml-1, P = 0.025. The infusion of calcitonin also stimulated 1,25(OH)2D levels compared with controls on a regular diet (80 +/- 17 vs. 38 +/- 6 pg . ml-1, P less than 0.05) and on a calcium-free diet (460 +/- 50 vs. 139 +/- 37 pg . ml-1, P less than 0.001). In addition, calcitonin increased plasma calcium levels in animals on a regular diet by 50%; this effect was most likely due to increased intestinal absorption of calcium, because removal of calcium from the diet markedly blunted this effect. In contrast, calcitonin administration did not significantly affect 25(OH)D plasma levels. Collectively, these data suggest that calcitonin and calcium are independent regulators of 1,25(OH)2D production and that calcitonin stimulates intestinal absorption of calcium, by increasing circulating levels of 1,25(OH)2D.

Topics: Animals; Calcitonin; Calcitriol; Calcium; Hydroxycholecalciferols; Hypocalcemia; Injections, Subcutaneous; Intestinal Absorption; Male; Phosphates; Rats; Rats, Inbred Strains; Time Factors

Hypocalcemia induced by salmon calcitonin (SCT) was evaluated in 125 patients with multiple myeloma (MM) and compared with 20 normal individuals (NCs) and 20 individuals with monoclonal gammopathy of undetermined significance (MGUS). It is now well documented that the maximum hypocalcemia (M delta CA) induced in man by SCT is related to the prevailing rate of osteoclastic resorption. In patients with MGUS, the level of M delta CA was normal. Conversely, the M delta CA was significantly abnormal in patients with MM (P less than .0001 for differences between NC/MGUS patients) and was correlated with (1) initial calcium levels (P less than .001), (2) the extent of lytic bone lesions (LBLs) (P less than .01), and (3) the myeloma cell mass (P less than .001) plus disease activity. The M delta CA was found to be of predictive value for new LBLs with or without hypercalcemia and to have dramatic influence on the survival of patients with MM. We conclude that the SCT-induced hypocalcemia test is of significant importance in the evaluation of the instantaneous rate of bone resorption and in the prognosis of patients with MM.

Topics: Adult; Aged; Bone Diseases; Calcitonin; Calcium; Female; Humans; Hypercalcemia; Hypocalcemia; Male; Middle Aged; Multiple Myeloma; Neoplasm Staging; Osteoclasts; Prognosis; Radiography; Radionuclide Imaging

Intracerebroventricular (i.c.v.) injection of 19 pmol/rat or more of salmon calcitonin (sCT) or iodinated sCT suppressed spontaneous intake of food and water in a dose-dependent manner. Tail-whipping was a peculiar behavior which concomitantly developed, but no analgesia ensued from the doses tested (up to 62 pmol/rat). It was examined how the rise and fall pattern of these behavioral effects would correlate with the dispositional pattern of 125I-sCT. When the radioactive peptide was injected in anorectic doses via the i.c.v. route, the radioactivity was found to distribute throughout the brain, but not uniformly. In rats which showed a marked anorexia and tail-whipping behavior, distribution occurred in such a manner that it could be interpreted to reflect the regional and subcellular distribution pattern of sCT-specific binding sites. Even 3 hr after injection, the hypothalamus, the smallest region, retained the highest radioactivity corresponding to about 1% of the dose and at least one half of which was identified as the intact iodo-sCT. To be noted is the finding that sCT injected centrally will quickly enter the systemic circulation and peripherally induced long-lasting hypocalcemia, since the anorectic dose of sCT is considerably higher than the dose needed for the peripheral effect. It is concluded that most of the sCT after i.c.v. injection leaks into the systemic circulation, but the rest is retained rather selectively around the receptor in hypothalamic nuclei for a long time, leading to day-long suppression of feeding and drinking behavior.

Topics: Animals; Appetite Depressants; Behavior, Animal; Brain; Calcitonin; Drinking; Eating; Hypocalcemia; Hypothalamus; Injections, Intraventricular; Iodine Radioisotopes; Kinetics; Male; Rats; Rats, Inbred Strains; Subcellular Fractions

Topics: Aged; Calcitonin; Calcium; Female; Humans; Hypocalcemia; Injections, Intravenous; Male