calcimycin and Pancreatic-Neoplasms

Pancreatic ductal and lung adenocarcinomas are the most common and prevalent types of human neoplasms with a greater than 80% mortality rate. The poor prognosis of both these cancers are likely due to the absence of valid approaches for early detection, the frequency of its metastases at the time of diagnosis, frequent recurrence after surgery, and poor responsiveness to chemotherapy. Most notably, the early development of pancreatic intraepithelial neoplasia and lung lesions is suggested to be the result of a mutation in the K-ras (G12D) oncogene. Tumor necrosis factor-related-apoptosis-inducing-ligand (TRAIL) has been shown to have great potential for the treatment of most human tumor cells, while leaving normal cells unharmed. However, some cancers show resistance to TRAIL treatment, leaving a gap in the understanding of its exact etiology.. TRAIL-induced resistance to cell death was investigated in pancreatic and lung cancer cell lines. Cell survival was determined by SRB and apoptosis by ELISA-based cell death assay. Activation of bid and caspases were evaluated by Western blotting.. Our study demonstrated that TRAIL significantly suppressed cell survival, by inducing apoptosis in a dose-dependent manner, in the pancreatic cancer BxPC-3 (wild type G12) and lung cancer A549 (G12S) cell lines. In contrast, Panc-1 pancreatic and SK-LU-1 lung cancer cell lines, which have a mutated (G12D) K-ras genotype, were resistant to the actions of TRAIL.. This study demonstrates an association between TRAIL resistance to apoptosis in human pancreatic and lung cancer cell lines and G12D K-ras(12) mutation.

Topics: Amino Acid Substitution; Apoptosis; BH3 Interacting Domain Death Agonist Protein; Calcimycin; Caspases; Cell Line, Tumor; Cell Survival; Drug Resistance, Neoplasm; Genes, ras; Humans; Lung Neoplasms; Pancreatic Neoplasms; Point Mutation; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Recombinant Proteins; TNF-Related Apoptosis-Inducing Ligand

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignant disease with poor long-term survival rates. Major reason for poor disease outcome is the profound intrinsic resistance of PDAC cells to currently available treatment regimens. We recently found that a great majority of PDAC tumors and tumor cell lines express high basal level of tissue transglutaminase (TG2), a multifunctional protein implicated in apoptosis, cell attachment, cell survival, and cell motility functions. Based on these observations, we hypothesized that activation of endogenous TG2 can induce spontaneous apoptosis in PDAC cells. The results obtained suggested that activation of endogenous TG2 by calcium ionophore A23187 induced rapid and spontaneous apoptosis in PDAC cells. TG2-induced apoptosis was associated with release of apoptosis-inducing factor (AIF). The release of AIF from mitochondria led to its translocation to the nucleus and subsequent apoptosis of PDAC cells in caspase-independent manner. In conclusion, our results provide first evidence that TG2 can induce apoptosis in PDAC cells in an AIF-dependent and caspase-independent manner.

Topics: Apoptosis; Apoptosis Inducing Factor; Calcimycin; Calcium Channels; Carcinoma, Pancreatic Ductal; Cell Death; Cell Differentiation; Deoxycytidine; Disease Progression; Gemcitabine; Gene Expression Regulation, Neoplastic; GTP-Binding Proteins; Humans; Ionophores; Models, Biological; Pancreatic Neoplasms; Protein Glutamine gamma Glutamyltransferase 2; Transglutaminases; Tumor Cells, Cultured

To elucidate the regulatory pathway through which pancreastatin inhibits insulin secretion, RINm5F insulinoma cells were challenged with physiological and pharmacological probes known to stimulate insulin release through different mechanisms. Utilizing the electrophysiological technique of capacitance measurements as a correlate to exocytosis, pancreastatin was found to significantly diminish maximum capacitance changes evoked by glyceraldehyde, an effect which was attenuated in pertussis toxin-treated cells. In static incubations of this cell line, pancreastatin significantly inhibited insulin secretion stimulated by glyceraldehyde, carbachol and A23187, secretagogues known to directly elevate beta-cell cytosolic Ca2+. This peptide also inhibited insulin secretion stimulated by phorbol myristate acetate (PMA), but only at incubation times < or = 15 min. It was without effect on insulin secretion stimulated by mastoparan and longer incubations (30 min) with PMA, where the secretory mechanisms are not necessarily Ca(2+)-dependent. Additionally, pancreastatin had no effect on carbachol-generated inositol phosphate accumulation but inhibited simultaneously stimulated insulin secretion. All inhibitory effects of pancreastatin were pertussis toxin sensitive. These results suggest that pancreastatin inhibits insulin secretion in RINm5F cells through a G-protein regulated mechanism at a control point involved in the Ca(2+)-directed exocytotic machinery, a feature shared by other physiologic inhibitors of insulin secretion.

Topics: Animals; Anti-Bacterial Agents; Calcimycin; Calcium; Carbachol; Chromogranin A; Exocytosis; Glyceraldehyde; GTP-Binding Proteins; Inositol Phosphates; Insulin; Insulin Secretion; Insulinoma; Intercellular Signaling Peptides and Proteins; Pancreatic Hormones; Pancreatic Neoplasms; Peptides; Pertussis Toxin; Phorbol Esters; Rats; Tumor Cells, Cultured; Virulence Factors, Bordetella; Wasp Venoms

Brief phorbol ester treatment of BON cells results in a persistent release and cellular depletion of immunoreactive chromogranin A (CGA-IR) and neurotensin (NT-IR) cell contents. The purpose of the present study was to characterize the effects of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on the secretion, biosynthesis, and steady-state messenger RNA (mRNA) levels of chromogranin A (CGA) and of a coresident peptide, neurotensin, by a novel human pancreatic carcinoid cell line, called BON. Acute TPA treatment (100 nM, 1 h) of BON cells resulted in 20- and 40-fold elevations in release of CGA-IR and NT-IR, respectively; and a 70-90% depletion of CGA-IR and NT-IR cell contents. TPA treatment also increased the biosynthetic rate of CGA-IR. Steady-state mRNA levels of CGA and NT/N (neurotensin/neuromedin N) were unchanged. Cell contents of CGA-IR and NT-IR were not replenished for a period of up to 6 days; secretion of CGA-IR and NT-IR persisted. In addition, BON cells failed to release CGA in response to stimulation by ionomycin and A23187 several days after acute TPA treatment. Our data indicate that the lack of replenishment of cell contents of CGA-IR and NT-IR is not due to decreases in steady-state CGA-IR and NT-IR mRNA levels, nor is it due to a decrease in biosynthesis of CGA-IR, but it is the result of a loss in the ability of TPA-treated BON cells to store and secrete CGA-IR and NT-IR in a regulated manner. These effects of TPA are mediated through the PKC pathway.

Topics: Analysis of Variance; Blotting, Northern; Calcimycin; Carcinoid Tumor; Cell Division; Cell Line; Chromogranin A; Chromogranins; Dose-Response Relationship, Drug; Gene Expression; Humans; Ionomycin; Kinetics; Methionine; Neurotensin; Pancreatic Hormones; Pancreatic Neoplasms; Peptide Fragments; RNA, Messenger; Sulfur Radioisotopes; Tetradecanoylphorbol Acetate; Time Factors; Tumor Cells, Cultured

The bile salt-stimulated cholesterol esterase is a digestive enzyme synthesized by the acinar cells of the pancreas. Previous results have shown that cholesterol esterase biosynthesis and secretion in the AR42J pancreatoma cells could be increased 3-5-fold by intestinal hormones such as cholecystokinin (CCK). The purpose of the current study is to explore the signalling mechanism by which CCK stimulation of AR42J cells results in increased biosynthesis and secretion of the cholesterol esterase. The results showed that the CCK-induced cholesterol esterase secretion could be mimicked by addition of the Ca2+ ionophore A23187 or by transient incubation of AR42J cells with the protein kinase C activator phorbol 12-myristate 13-acetate (PMA). Cholesterol esterase stimulation by CCK, A23187 and PMA could be abolished by the calcium chelator BAPTA or by specific protein kinase C inhibitors such as chelerythrine. Additionally, prolonged incubation of AR42J cells with PMA to reduce the protein kinase C level, also reduced CCK-stimulated cholesterol esterase secretion to a level similar to that observed in control cells. Taken together, these data suggested that CCK activation of cholesterol esterase secretion may be mediated by a Ca(2+)-dependent protein kinase C pathway, requiring increases in calcium mobilization and activation of protein kinase C.

Topics: Animals; Calcimycin; Calcium; Cholecystokinin; Egtazic Acid; Enzyme Activation; Pancreas; Pancreatic Neoplasms; Protein Kinase C; Rats; Sterol Esterase; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

In order to study the role of arachidonic acid (AA) in depolarization-induced insulin secretion rat insulinoma cells (RINm5F) were depleted of AA by cultivation in essential fatty acid-free medium. Within 2 weeks AA content of these cells was decreased to a non-detectable level as assessed by gas chromatography (GC). Different cell lines were obtained by supplementation of the defatted medium with oleic acid or the AA precursor linoleic acid (7 and 70 microM, each). The AA content varied in dependence from the precursor availability from 0 to about 14% of long chain fatty acids. Variation in AA content or the depletion of AA to a non-detectable level did not modulate insulin synthesis, basal and potassium-induced insulin release, cell growth (cell number and protein), membrane depolarization and increases in cytosolic Ca2+. In AA containing cells no eicosanoids was produced in the course of stimulated hormone release. The data suggest that in RINm5F cells release of AA and/or formation of oxidized metabolites from AA are not essential for functional integrity.

Topics: Alanine; Animals; Arachidonic Acid; Calcimycin; Calcium; Cell Division; Insulin; Insulin Secretion; Insulinoma; Lipoxygenase; Membrane Potentials; Pancreatic Neoplasms; Potassium Chloride; Prostaglandin-Endoperoxide Synthases; Rats; Tumor Cells, Cultured

It is found that secretion of pancreastatin and somatostatin from QGP-1N cells is regulated through muscarinic receptor-mediated activation of phosphatidylinositide hydrolysis system. In this report, whether the cAMP pathway interacts with the phosphoinositide turnover system for the secretion of pancreastatin and somatostatin from QGP-1N cells through muscarinic receptors was studied. Stimulation of QGP-1N cells with carbachol increased intracellular cAMP levels. The carbachol-induced increase in cAMP levels was inhibited by atropine. Calcium ionophore (A23187) and phorbol 12-myristate 13-acetate increased cAMP synthesis. Dibutyryl cAMP, forskolin and theophylline stimulated secretion of pancreastatin and somatostatin. When either dibutyryl cAMP, forskolin or theophylline was added in culture medium with A23187, phorbol ester or carbachol, a synergistic effect was found on pancreastatin and somatostatin secretion. These results suggest that interaction between the phosphoinositide turnover system and the cAMP pathway occurs in QGP-1N cells through muscarinic receptor stimulation for the secretion of pancreastatin and somatostatin.

Topics: Adenoma, Islet Cell; Atropine; Bucladesine; Calcimycin; Carbachol; Cell Line; Chromogranin A; Colforsin; Cyclic AMP; Drug Synergism; Humans; Kinetics; Pancreatic Hormones; Pancreatic Neoplasms; Phosphatidylinositols; Somatostatin; Tetradecanoylphorbol Acetate; Theophylline; Tumor Cells, Cultured

Studies were made of pancreastatin (PST) secretion from a human PST-producing cell line (QGP-1N) in response to various secretagogues. Cells with immunoreactivity for PST were observed in monolayer cultures of QGP-1N cells. Carbachol stimulated PST secretion and the intracellular Ca2+ mobilization concentration dependently in the range of 10(-6)-10(-4) M. The PST secretion and Ca2+ mobilization induced by carbachol were inhibited by atropine. The calcium ionophore (A23187) stimulated PST secretion. However, cholecystokinin and gastrin-releasing peptide did not stimulate either PST secretion or Ca2+ mobilization. Secretin also did not stimulate PST secretion. The glucose concentration in the culture medium had no effect on PST secretion. These results suggest that PST secretion is mainly regulated by acetylcholine through a muscarinic receptor, and that an increase in intracellular Ca2+ plays an important role in stimulus-secretion coupling in QGP-1N cells.

Topics: Acetylcholine; Adenoma, Islet Cell; Atropine; Calcimycin; Calcium; Carbachol; Chromogranin A; Gastrin-Releasing Peptide; Humans; Pancreatic Hormones; Pancreatic Neoplasms; Parasympatholytics; Peptides; Piperidines; Pirenzepine; Receptors, Muscarinic; Sincalide; Tumor Cells, Cultured

Receptor currents generated in response to the application of sulfated octa-cholecystokinin (CCK) and various pancreatic secretagogues were studied in AR42J cells, a rat pancreatic acinar cell line. A whole cell configuration of the patch electrode voltage-clamp technique was utilized in these studies. Over 60% of the cells examined responded to 10(-6) M CCK by generating inward current at a membrane holding potential of -70 mV, accompanied by an increased membrane conductance. The CCK-induced receptor current (ICCK) was typically inactivated within 30 s in the presence of the ligand. The reversal potential (Erev) of the ICCK was approximately 0 mV when recorded in control bathing solution with a pipette containing 154 mM Cl-. When Cl- concentration in the bathing solution or in the recording pipette was modified, the Erev of the ICCK shifted toward the predicted Cl- potential. Na+ and K+ did not show significant contributions to the Erev of ICCK. Hence, the ICCK involves an increased Cl- conductance. This increased Cl- conductance appears to be due to an increase in intracellular Ca2+, since the ICCK could not be recorded from cells using pipettes containing 5 mM EGTA. Application of a Ca2+ ionophore A23187 (5 microM) to cells in control saline induced a similar inward current flow. The source of the Ca2+ involved in the ICCK appears to be mainly intracellular, since the ICCK could be recorded under conditions designed to completely block the voltage-dependent Ca2+ entry. These included exposure of the cells to a Ca2(+)-free saline for a brief period or the presence of 500 microM Cd2+ in the control bathing solution.

Topics: Animals; Calcimycin; Calcium Channels; Cell Line; Chlorides; Cholecystokinin; Egtazic Acid; Kinetics; Membrane Potentials; Mice; Pancreas; Pancreatic Neoplasms; Rats; Receptors, Cholecystokinin; Sodium

The photodynamic effects of sulphonated aluminium phthalocyanine (SALPC) have been compared on cultured AR4-2J cells of a pancreatic carcinoma cell line and on exocrine cells of the normal phenotype freshly isolated from the rat pancreas; a multi-channel perifusion system was used for this kinetic study in vitro. Whereas light alone or SALPC alone was without effect on either cell type, photon activation of cellularly-bound SALPC with light greater than 570 nm permeabilised the cells and caused an increase in amylase secretion from normal acinar cells but a dose-dependent inhibition (10(-7) to 10(-5) M) of amylase release from AR4-2J cells. In contrast, direct permeabilisation of the plasma membrane with digitonin, 10 micrograms ml-1, evoked a marked release of amylase from both types of cell. Elevation of [Ca2+]i by the ionophore A23187, 10(-6) M, elicited secretion of amylase from normal cells but had little effect on AR4-2J cells. Finally, it was established that the differential photodynamic effects of SALPC on amylase release were not attributable to any topographical differences in the microanatomical organisation of normal or tumour-derived cells; furthermore, the structural integrity of normal and AR4-2J cells was maintained after the photodynamic action of SALPC. It is concluded that the generation of singlet oxygen is responsible for permeabilisation of both types of cell and that photon-activated SALPC has functionally distinct effects on the constitutive secretion of amylase of tumour cells and the regulated secretory pathway of normal cells. These observations may be important in the development of drugs with a selective photodynamic action on pancreatic tumour cells.

Topics: Amylases; Animals; Calcimycin; Cell Line; Cell Membrane Permeability; Dexamethasone; Digitonin; Dose-Response Relationship, Drug; Indoles; Organometallic Compounds; Pancreatic Neoplasms; Photochemotherapy; Rats; Tumor Cells, Cultured

Vasoactive intestinal peptide-producing tumor tissue fragments obtained at surgery were maintained in short-term culture. Functional cellular integrity of vasoactive intestinal peptide-producing tumor tissue was reflected by progressive protein synthesis and the ability of tumor tissue to release vasoactive intestinal peptide when stimulated by the intracellular second messengers cyclic adenosine monophosphate and calcium. Studies with verapamil and ethyleneglycol-bis (beta-aminoethylether)-N,N'-tetraacetic acid suggest that cyclic nucleotide- and ionophore A23187-mediated vasoactive intestinal peptide release are dependent, at least in part, upon the availability and transmembrane transport of extracellular calcium.

Topics: 1-Methyl-3-isobutylxanthine; Adenoma, Islet Cell; Calcimycin; Calcium; Cells, Cultured; Cyclic AMP; Egtazic Acid; Female; Humans; Immunohistochemistry; Leucine; Middle Aged; Pancreatic Neoplasms; Radioimmunoassay; Vasoactive Intestinal Peptide; Verapamil; Vipoma

Gastrinoma cells from surgical specimens of a primary pancreatic tumor and an hepatic metastasis in two patients with a Zollinger-Ellison syndrome were grown and subcultured for 7 mo. Cultured cells displayed a strong reactivity to heptadecapeptide gastrin antibody and maintained an ultrastructural appearance resembling that of the original tumor cells with the presence of secretory granules of variable size and electron density. Cultured cells also showed the ability to secrete immunoreactive gastrin, and this secretion was further concentration-dependently stimulated by secretin (10(-10)-10(-6) M), carbachol (10(-6) M), and bombesin (10(-10)-10(-6) M). The latter peptide was the more potent stimulant with a maximal effect at 10(-9) M (460 +/- 20% of basal release; P less than 0.05). This stimulation occurred in the absence of extracellular Ca2+ and was potentiated by the addition of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP; 10(-3) M) into the culture medium. The somatostatin analogue, somatostatin-(201-995), did not alter basal gastrin release but inhibited secretin, carbachol, and bombesin stimulation. Moreover, DBcAMP (10(-3) M) and Ca2+ (1-3 mM) stimulated gastrin release; Ca2+ ionophore A23187 (6 micrograms/ml) enhanced gastrin response to Ca2+ in the early time intervals of incubation. Furthermore the phorbol ester derivative, 12-O-tetradecanoyl phorbol-13-acetate, dramatically stimulated gastrin release (10 times the basal value). We conclude that gastrinoma cells can be cultured over an extended period with maintenance of their capacity to secrete gastrin in response to various hormones and mediators.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Bombesin; Bucladesine; Calcimycin; Calcium; Carbachol; Culture Media; Gastrinoma; Gastrins; Humans; In Vitro Techniques; Liver Neoplasms; Pancreatic Neoplasms; Secretin; Stimulation, Chemical; Tumor Cells, Cultured

The cell line In-R1-G9 is one of the clones from the hamster insulinoma cell line, In-111-R1, and it produces glucagon. Phorbol esters markedly enhanced glucagon secretion and the stimulatory effect was found to be correlated to their biological activity as tumor promoters. At a concentration of 200 nM, 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated glucagon secretion 13-fold more than the control in 10 min. The effect of TPA was not influenced by actinomycin D, cycloheximide, colchicine or vincristine. Depletion of calcium from the incubation medium inhibited TPA-induced glucagon secretion by approximately 50% and dibucaine also suppressed glucagon secretion to 67.4%. An addition of A23187 to TPA induced 150% enhancement over the TPA-stimulated glucagon level, and the maximum secretory response was observed when the cells were stimulated with the simultaneous addition of TPA, A23187 and theophylline.

Topics: Adenoma, Islet Cell; Animals; Calcimycin; Cell Line; Clone Cells; Cricetinae; Drug Synergism; Glucagon; In Vitro Techniques; Insulinoma; Pancreatic Neoplasms; Phorbols; Tetradecanoylphorbol Acetate; Theophylline

Regulation of endoplasmic reticulum (ER) Ca2+ cycling by inositol 1,4,5-trisphosphate (IP3) was studied in saponin-permeabilized RINm5F insulinoma cells. Cells were incubated with mitochondrial inhibitors, and medium Ca2+ concentration established by nonmitochondrial pool(s) (presumably the ER) was monitored with a Ca2+ electrode. IP3 degradation accounted for the transience of the Ca2+ response induced by pulse additions of the molecule. To compensate for degradation, IP3 was infused into the medium. This resulted in elevation of [Ca2+] from about 0.2 microM to a new steady state between 0.3 and 1.0 microM, depending on both the rate of IP3 infusion and the ER Ca2+ content. The elevated steady state represented a bidirectional buffering of [Ca2+] by the ER, as slight displacements in [Ca2+], by small aliquots of Ca2+ or the Ca2+ chelator quin 2, resulted in net uptake or efflux of Ca2+ to restore the previous steady state. When IP3 infusion was stopped, [Ca2+] returned to its original low level. Ninety per cent of the Ca2+ accumulated by the ER was released by IP3 when the total Ca2+ content did not exceed 15 nmol/mg of cell protein. Above this high Ca2+ content, Ca2+ was accumulated in an IP3-insensitive, A23187-releasable pool. The maximal amount of Ca2+ that could be released from the ER by IP3 was 13 nmol/mg of cell protein. The data support the concept that in the physiological range of Ca2+ contents, almost all the ER is an IP3-sensitive Ca2+ store that is capable of finely regulating [Ca2+] through independent influx (Ca2+-ATPase) and efflux (IP3-modulated component) pathways of Ca2+ transport. IP3 may continuously modulate Ca2+ cycling across the ER and play an important role in determining the ER Ca2+ content and in regulating cytosolic Ca2+ under both stimulated and possibly basal conditions.

Topics: Adenoma, Islet Cell; Animals; Calcimycin; Calcium; Cell Line; Cell Membrane Permeability; Endoplasmic Reticulum; Inositol 1,4,5-Trisphosphate; Inositol Phosphates; Insulinoma; Kinetics; Mitochondria; Pancreatic Neoplasms; Rats; Subcellular Fractions; Sugar Phosphates

Dispersed single-cell suspensions of human gastrinoma tissue were incubated for 15, 60, and 120 min in a calcium-containing medium, (0.1, 2, 10 mM) in calcium-free medium and in calcium-free medium containing the calcium ionophore A23187 (0.01, 1, and 100 micrograms/ml). Supernatant and pellet (intracellular) gastrin levels were determined by radioimmunoassay. Supernatant gastrin levels remained stable over 120 min in calcium chloride or calcium gluconate containing medium, while intracellular pellet gastrin approximately tripled during the same incubation period. Total gastrin (supernatant plus pellet) approximately doubled during the 2-hr incubation in calcium. However, calcium (0.1, 2, or 10 mM) failed to produce a dose-dependent rise in supernatant, pellet, or total gastrin when compared to calcium-free incubates. Contrary to the expected gastrin response to calcium, supernatant and pellet gastrin levels were higher in incubates in calcium-free medium than in calcium-containing incubates. A23187 (0.01 or 1 mcg/ml) in a calcium-free medium decrease supernatant gastrin while high dose ionophore (100 mcg/ml) increased supernatant gastrin. All doses of ionophore stimulated pellet and total gastrin levels. Thus, it appears that the clinical augmentation of gastrin levels, seen with calcium challenge in vivo may not be solely due to changes in serum calcium.

Topics: Adult; Calcimycin; Calcium; Cytological Techniques; Gastrins; Humans; Male; Pancreatic Neoplasms; Zollinger-Ellison Syndrome

The regulation of extramicrosomal Ca2+ concentration maintained by suspensions of rat insulinoma microsomes was studied using Ca2+-selective minielectrodes. The Ca2+-transporting activity was MgATP dependent and correlated with the endoplasmic reticulum marker NADPH-cytochrome c reductase. When incubated in a high KCl medium containing Mg2+ and phosphate, the microsomes lowered [Ca2+] within less than 10 min to around 0.2 microM. They had a high Ca2+-sequestering activity since they were able to take up and retain several small Ca2+ additions. No evidence for a Na+/Ca2+ countertransport was obtained. The accumulated Ca2+ was released by the Ca2+ ionophore A23187 or upon transforming ATP into ADP using glucose plus hexokinase. The addition of ADP, at concentrations present in cells, resulted in a dose-dependent and reversible net Ca2+ efflux from the microsomes until a higher [Ca2+] steady state was reached. This was specific for ADP since GDP, UDP, CDP, IDP, and the nonhydrolyzable analogue methylene-ADP as well as AMP and cAMP did not reproduce the effect. Insulin secretory granules were unable to lower medium [Ca2+] or to take up a pulse addition of Ca2+. However, most of the large granular calcium content was released by A23187. The addition of Na+ and lowering or increasing medium pH by 0.2 pH unit did not induce Ca2+ uptake or efflux from the secretory granules. The results indicate that insulinoma endoplasmic reticulum but not insulin secretory granules may play a critical role in the regulation of cytosolic Ca2+. A variation in cellular ADP content following secretagogue addition might modulate Ca2+ fluxes across the endoplasmic reticulum and contribute in raising cytosolic Ca2+.

Topics: Adenoma, Islet Cell; Animals; Biological Transport, Active; Calcimycin; Calcium; Calcium-Transporting ATPases; Cell Fractionation; Cell Line; Cytoplasmic Granules; Endoplasmic Reticulum; Insulin; Insulin Secretion; Insulinoma; Kinetics; Microsomes, Liver; Organoids; Pancreatic Neoplasms; Rats; Rats, Inbred Strains

The secretion of protein, like cell proliferation, is an integrated response that reflects structural organization of the cell periphery. Stimulation of protein secretion was thus utilized for comparison of integrated responses of the cell periphery in pancreatic acinar carcinoma of the rat and integrated responses in normal rat pancreas. Results of this comparison include: a) The stimulation of protein secretion in acinar carcinoma fragments by carbamylcholine chloride and cholecystokinin octapeptide, pancreatic secretagogues that interact with specific plasma membrane receptors, was only a fraction (one-fifth to one-half) of that observed in normal pancreatic minilobules. b) The Ca2+ ionophore A23187 and the cyclic nucleotide N6,O2'-dibutyryl cyclic AMP, secretagogues that act independently of specific membrane receptors, did not stimulate secretion in the acinar carcinoma. The observed quantitative and qualitative differences in protein secretion indicate fundamental differences in cell periphery organization between the normal and transformed acinar cells of pancreas.

Topics: Animals; Bucladesine; Calcimycin; Carbachol; Carcinoma; Cell Membrane; Cholecystokinin; Dose-Response Relationship, Drug; In Vitro Techniques; Pancreas; Pancreatic Neoplasms; Peptide Fragments; Proteins; Rats; Secretory Rate; Sincalide; Temperature