l-365260 and gastrin-17

Gastrin contributes to the growth and proliferation of gastric cancer cells and it is related to the effect of tyrosine kinase. This study was to investigate the effect of gastrin on tyrosine phosphorylation of focal adhesion kinase (FAK) in human gastric cancer cell line SGC7901.. The vector pCR3.1/GR, that expresses human gastrin receptor (GR) stably, was transfected into SGC7901 cells (SGC7901-GR). The expression of GR was tested by reverse transcription-polymerase chain reaction (RT-PCR). SGC7901-GR and SGC7901 cells were treated with L-365260, an antagonist of GR, and stimulated with gastrin at different concentrations for different time. The tyrosine phosphorylation level of FAK was detected by immunoprecipitation and Western blot.. When treated with different concentrations of gastrin for 1 min, the tyrosine phosphorylation levels of FAK were significantly higher in SGC7901-GR cells than in SGC7901 cells (0.64+/-0.06 vs. 0.40+/-0.05 at 0.1 nmol/L, 0.91+/-0.10 vs. 0.52+/-0.07 at 1 nmol/L, and 1.00+/-0.10 vs. 0.62+/-0.06 at 10 nmol/L, P<0.01). When treated with 10 nmol/L gastrin for different time, the tyrosine phosphorylation levels of FAK were also significantly higher in SGC7901-GR cells than in SGC7901 cells (0.72+/-0.08 vs. 0.59+/-0.05 at 1 min, 0.83+/-0.05 vs. 0.65+/-0.07 at 5 min, 0.88+/-0.06 vs. 0.58+/-0.03 at 10 min, and 1.00+/-0.08 vs. 0.47+/-0.10 at 20 min, P<0.05). L-365260 decreased the tyrosine phosphorylation levels of FAK from 1.00+/-0.07 to 0.72+/-0.07 in SGC7901-GR cells (P<0.01), and from 0.62+/-0.06 to 0.45+/-0.05 in SGC7901 cells (P<0.01). The protein levels of FAK in different cells remained unchanged during these experiments (P>0.05).. FAK is a pivotal signal transducer in downstream of gastrin with GR. Tyrosine phosphorylation is the symbol of FAK activation.

Topics: Benzodiazepinones; Cell Line, Tumor; Focal Adhesion Kinase 1; Gastrins; Genetic Vectors; Humans; Phenylurea Compounds; Phosphorylation; Receptor, Cholecystokinin B; Signal Transduction; Stomach Neoplasms; Transfection

To explore the molecular mechanism of increasing the invasion of colon cancer cells by gastrin 17.. The plasmid pCR 3.1/GR expressing the gastrin receptor cholecystokinin-2 receptor (CCK-2R) was transfected into colonic carcinoma cells of the line Colo320 by Lipofectamine 2000. The clones expressing stably CCK-2R were screened by G418 and named as Colo320WT cells. The expression levels of gastrin receptor of the Colo320 and Colo320WT cells were assayed by RT-PCR and Western blotting. The Colo320WT cells were treated by gastrin-17, and the expression levels of phosphorylated FAKTyr397 and total focal adhesion kinase (FAK) in the Colo320WT cells at the time points 0, 1, 6, 12, 24, and 48 h were detected by Western blotting. Another Colo320WT cells were treated by L365, 260, gastrin17 receptor blocker, for 30 minutes firstly and then treated by gastrin17 again for 12 hours, and then Western blotting was used to detect the expression levels of phosphorylated FAKTyr397 and total focal adhesion kinase (FAK) at the time points 0, 1, 6, 12, 24, and 48 h. Confocal microscopy was used to observe the phosphorylated FAKTyr397 localizing in the lamellipodia. The information of FAK-Src-p130(Cas)-Dock180 signaling complex was assayed by coimmuniprecipation and immunity blotting. The level of Rac-GTPase was tested by pull down assay.. The level of phosphorylated FAKTyr397 expression in the Colo320WT cells after the gastrin17 intervention increased time-dependently and peaked at the time point of 12 h, and the phosphorylated FAKTyr397 expression in the Colo320WT cells treated by L365, 260 decreased remarkably, but the level of total FAK remained unchanged. The phosphorylated FAKTyr397/FAK levels were 2.82%, 9.28%, 22.62%, 38.59%, 28.41%, and 14.94%, 0, 1, 6, 12, 24, and 48 h after the gastrin17 treatment respectively, and the level was 7.21% after L365, 260 treatment. The amount of phosphorylated FAKTyr397 localizing in the lamellipodia of the Colo320WT cells that were treated by gastrin17 increased time-dependently and peaked at the time-point 12 h. FAK-Src-p130(Cas)-Dock180 signaling complex was formed in the Colo320WT cells stimulated with gastrin17. Gastrin17 activated Rac, but did not affect the total Rac expression.. The mechanism of increasing the colon cancer cells' invasion by gastrin17 is probably that gastrin17 makes FAK-Tyr397 phosphorylated and be localized to lamellipodia, causes the forming of FAK-Src-p130(Cas)-Dock180 signaling complex when it is bound to its receptor CCK-2, and activation of Rac.

Topics: Benzodiazepinones; Blotting, Western; Cell Line, Tumor; Cell Movement; Colonic Neoplasms; Focal Adhesion Protein-Tyrosine Kinases; Gastrins; Humans; Neoplasm Invasiveness; Phenylurea Compounds; Phosphorylation; Receptor, Cholecystokinin B; Reverse Transcriptase Polymerase Chain Reaction; Transfection; Tyrosine

This study aims to investigate the role of gastrin-17 (G17) on angiogenesis features in gliomas both in vitro and in vivo.. The influences of G17 and G17 receptor antagonists were characterized in vitro in terms of angiogenesis on human umbilical vein endothelial cell (HUVEC) tubulogenesis processes on Matrigel and in vivo with respect to U373 orthotopic glioma xenografts. The influence of phosphatidylinositol 3'-kinase, protein kinase C, and nuclear factor-kappaB inhibitors was characterized in vitro on G17-mediated HUVEC tubulogenesis. G17-mediated release of interleukin (IL)-8 from HUVECs and G17-induced modifications in nuclear factor-kappaB DNA binding activity were characterized by means of specific enzyme-linked immunosorbent assays. The influence of G17 on E- and P-selectin expression was determined by means of computer-assisted microscopy, whereas the influence of E- and P-selectin on HUVEC migration was approached by means of antisense oligonucleotides. The chemotactic influence of G17 and IL-8 on HUVEC migration was characterized by means of computer-assisted videomicroscopy with Dunn chambers.. Messenger RNAs for cholecystokinin (CCK)A, CCKB, and CCKC receptors were present in HUVECs and microvessels dissected from a human glioblastoma. Whereas G17 significantly increased the levels of angiogenesis in vivo in the U373 experimental glioma model and in vitro in the HUVECs, the CCKB receptor antagonist L365,260 significantly counteracted the G17-mediated proangiogenic effects. G17 chemoattracted HUVECs, whereas IL-8 failed to do so. IL-8 receptor alpha (CXCR1) and IL-8 receptor beta (CXCR2) mRNAs were not detected in these endothelial cells. Gastrin significantly (but only transiently) decreased the level of expression of E-selectin, but not P-selectin, whereas IL-8 increased the expression of E-selectin. Specific antisense oligonucleotides against E- and P-selectin significantly decreased HUVEC tubulogenesis processes in vitro on Matrigel.. The present study shows that gastrin has marked proangiogenic effects in vivo on experimental gliomas and in vitro on HUVECs. This effect depends in part on the level of E-selectin activation, but not on IL-8 expression/release by HUVECs.

Topics: Animals; Benzodiazepinones; Brain Neoplasms; Cell Movement; Collagen; Drug Combinations; E-Selectin; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Female; Gastrins; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Glioblastoma; Humans; In Vitro Techniques; Interleukin-8; Laminin; Mice; Mice, Nude; Neovascularization, Pathologic; NF-kappa B; P-Selectin; Phenylurea Compounds; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Kinase C; Proteoglycans; Rats; Rats, Nude; Receptors, Cholecystokinin; Receptors, Interleukin-8A; Receptors, Interleukin-8B; Transplantation, Heterologous; Tumor Cells, Cultured; Umbilical Veins

This report describes the molecular cloning and pharmacological characterization of a transiently expressed chicken brain cholecystokinin receptor (CCK-CHR) in COS-7 cells. A polymerase chain reaction (PCR)-based cloning strategy was applied using: (1) an initial PCR with deoxyinosine-containing primers designed to target conserved regions in CCK receptors, followed by (2) rapid amplification of cDNA ends (RACE), and (3) full-length PCR of the CCK-CHR cDNA. The full-length cloned bicistronic CCK-CHR cDNA contained a short upstream open reading frame (uORF) coding for a putative six-amino-acid-long peptide of unknown function, followed by a long open reading frame (lORF) encoding the 436-amino-acid-long CCK-CHR receptor protein. At the amino acid level, the CCK-CHR shared approximately 50% homology with mammalian and Xenopus laevis CCK receptors. The pharmacological profile of CCK-CHR resembled that of CCK-B receptors using agonists (CCK-8, CCK-4, gastrin-17), whereas CCK-CHR showed higher affinity for the CCK-A receptor antagonist, devazepide, than for the CCK-B receptor antagonist, L-365,260. To the best of our knowledge, this is the first description and functional expression study of a cloned chicken CCK receptor cDNA.

Topics: Amino Acid Sequence; Animals; Benzodiazepinones; Brain; Chickens; Cloning, Molecular; COS Cells; Devazepide; DNA, Complementary; Gastrins; Inosine; Molecular Sequence Data; Phenylurea Compounds; Polymerase Chain Reaction; Radioligand Assay; Receptors, Cholecystokinin; RNA, Messenger; Sequence Homology, Amino Acid; Sincalide; Tetragastrin

There is increasing evidence for a direct interaction of the enteric nervous and immune system. Receptors for neuropeptides such as VIP, somatostatin, and substance P have been characterised in human immuno-haematopoietic cells but little is known about the functional significance and expression of receptors for cholecystokinin (CCK) on cells of the immune system. There are only few studies that describe the expression of CCK receptors on human leukaemia-derived cell lines but the receptor structure and function in normal leukocytes have not been clearly established. We therefore sought to determine CCK receptor expression, structure, and function in nontransformed human peripheral blood mononuclear cells.Full-length cDNA clones encoding the human CCK-A and CCK-B/gastrin receptor are expressed in peripheral blood mononuclear cells from healthy volunteers without haematopoietic malignancy. In addition to wild-type CCK-B/gastrin receptor cDNAs, we isolated a splice variant with an in frame insertion of 69 amino acids within its putative third intracellular receptor loop. Dideoxy sequence analysis revealed that the cDNA of this splice variant comprises exons 1-4 but retains intron 4 (207 bp) in the absence of mutations within the splice donor sites. Transient expression of this splice variant in COS-7 cells reveals wild-type affinity for CCK-8, Gastrin-17, and antagonist L-365,260. Affinity for glycine-extended gastrin-17 was not increased when compared to the wild-type CCK-B/gastrin receptor. In vitro, gastrin decreased 3H-thymidine labelling in phytohaemagglutinin-pretreated mononuclear cells at a half-maximally effective concentration of 1.5 nM. We also isolated a cDNA encoding another splice variant of the CCK-B/gastrin receptor with a 158 bp deletion of the entire exon 4 sequence. We conclude that wild-type transcripts of both CCK receptor subtypes and splice variants of the CCK-B/gastrin receptor are expressed in nontransformed human mononuclear cells and that gastrin exhibits antiproliferative effects.

Topics: Alternative Splicing; Amino Acid Sequence; Animals; Base Sequence; Benzodiazepinones; Binding, Competitive; Cell Division; Cloning, Molecular; COS Cells; Gastrins; Humans; Leukocytes, Mononuclear; Lymphocyte Activation; Molecular Sequence Data; Phenylurea Compounds; Radioligand Assay; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sequence Analysis, DNA; Sincalide; Transcription, Genetic; Transfection

We report here the cloning and characterization of a 5'-end alternatively spliced human cholecystokinin-B (CCK-B) receptor mRNA. The 5'-end of this CCK-B receptor transcript (termed CCK-BRtx) consisted of exon Ia, present in the ordinary full-length CCK-B receptor mRNA (CCK-BRwt), and exon Ib, present in a previously described 5'-end alternatively spliced CCK-B receptor mRNA (CCK-BRt). A short open reading frame preceded the AUG translation initiation codon of the CCK-BRtx. Transfection of COS-7 cells with the CCK-BRtx or CCK-BRt cDNAs did not lead to the appearance of peptidergic and non-peptidergic binding sites. Cell free in vitro translation yielded proteins of approximately 44 kDa (CCK-B receptor) and 40 kDa (CCK-BRt receptor) whereas no 40 kDa product was detected from the cloned CCK-BRtx cDNA. Instead, a protein product of approximately 9 kDa was visualized, the size corresponding to the predicted protein encoded by the short open reading frame. The alternatively spliced CCK-B receptor transcripts were concomitantly expressed with the ordinary full-length CCK-B receptor mRNA in the brain, pancreas, and stomach. The possibility that such transcripts are translated in vivo into truncated CCK-B receptors is discussed.

Topics: Alternative Splicing; Amino Acid Sequence; Animals; Base Sequence; Benzodiazepinones; Binding, Competitive; Cholecystokinin; Cloning, Molecular; COS Cells; Gastrins; Humans; Molecular Sequence Data; Phenylurea Compounds; Protein Binding; Protein Biosynthesis; Receptors, Cholecystokinin; RNA, Messenger; Sequence Analysis, DNA; Transfection

1. Cholecystokinin (CCK) and gastrin both stimulate gastric somatostatin (SOM) secretion in vitro and thus have the potential to modulate their direct effects on the parietal cell. However, the relative potencies and the mechanisms of action of CCK and gastrin on SOM secretion in vivo have not been determined. 2. The objectives of the present study were to compare the in vivo potencies of the sulphated(s) and non-sulphated (ns) forms of gastrin heptadecapeptide (G-17) and CCK octapeptide (CCK-8) on SOM secretion, and to determine the nature of the receptors involved by repeating the studies in the presence of the CCK-A and CCK-B/gastrin receptor antagonists L-364,718 and L-365,260, respectively. All experiments were performed in the chronically cannulated sheep. 3. Dose-response experiments revealed the following potencies for SOM secretion: G-17s = CCK-8s > G-17 ns >> CCK-8ns. However, based on the plasma levels achieved and a higher metabolic clearance rate (MCR) for CCK, CCK-8s was the most potent. 4. Both the CCK-A and CCK-B/gastrin receptor antagonists suppressed CCK-8s-stimulated SOM output. In contrast, G-17s-stimulated SOM output was inhibited by only the CCK-B/gastrin receptor antagonist. 5. Both receptor antagonists increased basal plasma gastrin and CCK levels. 6. The predominant circulating SOM molecular form after both gastrin and CCK stimulation was SOM-14. 7. In conclusion, the sulphated forms of CCK and gastrin are more potent than the non-sulphated forms. Despite sharing a common biologically active carboxy terminus, CCK stimulates SOM secretion by both the CCK-A and CCK-B/gastrin receptors, while gastrin acts via the CCK-B/gastrin receptor alone. These findings explain in part why CCK is a net inhibitor of gastric acid secretion in vivo.

Topics: Animals; Benzodiazepinones; Cholecystokinin; Chromatography, High Pressure Liquid; Devazepide; Drug Interactions; Gastric Mucosa; Gastrins; Hormone Antagonists; Infusions, Intravenous; Phenylurea Compounds; Receptor, Cholecystokinin A; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sheep; Sincalide; Somatostatin

We compared the responses of rat stomach ornithine decarboxylase (ODC) and histidine decarboxylase (HDC) to food intake, oral treatment with antisecretagogues, NaHCO3, and hypertonic NaCl, antrectomy, intravenous infusion of gastrin-17, the selective cholecystokinin (CCK)-B/gastrin receptor antagonist L-365,260, and the somatostatin analogue RC-160. The serum gastrin concentration and oxyntic mucosal ODC and HDC activities were higher in freely fed rats than in fasted rats. Food intake in fasted rats raised the serum gastrin concentration and the ODC and HDC activities. Ranitidine, omeprazole, and NaHCO3 raised the serum gastrin concentration and activated ODC and HDC. Hypertonic NaCl raised the ODC activity 200-fold, whereas circulating gastrin and HDC activity were increased only moderately. Infusion of gastrin-17 activated HDC but not ODC. L-365,260 prevented the activation of HDC but not of ODC in response to food intake and treatment with omeprazole, NaHCO3, or hypertonic NaCl. Antrectomy prevented the food- and omeprazole-evoked rise in oxyntic mucosal HDC activity but not the rise in ODC activity. RC-160 suppressed HDC activity after food intake and treatment with omeprazole, NaHCO3, or NaCl. In contrast, RC-160 suppressed omeprazole- and NaHCO3-evoked ODC activation but not that evoked by food intake or NaCl. The results support the view that HDC in the oxyntic mucosa is activated by gastrin and suppressed by somatostatin. The induction of ODC is not mediated by gastrin; ODC activation appears to be related to acid inhibition per se or to mucosal maintenance and repair; somatostatin, or rather the lack of it, might contribute to the induction of ODC after acid blockade. The mechanism behind the activation of rat stomach ODC seems to differ depending on the type of stimulus.

Topics: Analgesics; Animals; Benzodiazepinones; Cholecystokinin; Duodenum; Eating; Enzyme Activation; Fasting; Gastrectomy; Gastric Mucosa; Gastrins; Histidine Decarboxylase; Infusions, Intravenous; Kinetics; Male; Omeprazole; Ornithine Decarboxylase; Phenylurea Compounds; Pyloric Antrum; Ranitidine; Rats; Rats, Sprague-Dawley; Saline Solution, Hypertonic; Sodium Bicarbonate; Somatostatin; Time Factors

The effect of gastrin on the enterochromaffin-like cells in the rat stomach is mediated by cholecystokinin (CCK)-B receptors and manifested as activation of histidine decarboxylase (HDC). The dipeptoids PD 136450, PD 135158, and PD 134308 are thought to be selective CCK-B receptor antagonists. The effects of the dipeptoids and of gastrin-17 and sulfated CCK-8 on rat stomach HDC activity were examined.. Drugs were infused intravenously or subcutaneously to fasted rats, and the HDC activity was determined.. The dipeptoids activated HDC with maximal responses (50%-60% of the maximal response to gastrin) at 1 mumol.kg-1.h-1. Rat gastrin-17 activated HDC maximally at 3 nmol.kg-1.h-1, and sulfated CCK-8 produced maximal response at 20 nmol.kg-1.h-1. The CCK-B receptor antagonist L-365,260 inhibited the HDC activation induced by gastrin, sulfated CCK-8, or the dipeptoids. The dipeptoids did not inhibit the gastrin-induced HDC activation.. Gastrin, sulfated CCK-8, and the dipeptoids activated rat stomach HDC. L-365,260 but not devazepide inhibited the HDC activation. Thus, the dipeptoids, which failed to inhibit the gastrin-induced HDC activation, act as CCK-B receptor agonists and not as antagonists. It is important to recognize this to ensure appropriate interpretation of data obtained with these drugs.

Topics: Animals; Benzodiazepinones; Devazepide; Enzyme Activation; Gastrins; Histidine Decarboxylase; Indoles; Ligands; Male; Meglumine; Phenethylamines; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Sincalide; Stomach

Functional studies suggest that guinea pig chief cells have both cholecystokinin-A (CCK-A) and CCK-B receptors (CCK-A-R and CCK-B-R, respectively). However, all efforts to directly characterize the specific CCK-A-R using binding have been unsuccessful. Recent studies describe specific CCK-A-R agonists such as A-71378 ([desamino-Nle28,31-(N-methyl)Asp32]CCK heptapeptide]. In the present study, [D-Tyr-Gly]A-71378 was synthesized, which has > 300-fold selectivity for CCK-A-R and can be iodinated. [D-Tyr-Gly]A-71378 was equipotent to A-71378 in stimulating pepsinogen release from purified guinea pig chief cells. Binding of 125I-labeled [D-Tyr-Gly]A-71378 was saturable and specific. Potencies for inhibiting binding were as follows: [D-Tyr-Gly]A-71378 = A-71378 = 4x CCK octapeptide (CCK-8) > 1,000x des(SO4)-CCK-8, gastrin. In contrast, for 125I-gastrin binding they were CCK-8 > gastrin-17-I > des(SO4)-CCK-8 >> A-71378 or [D-Tyr-Gly]A-71378. Binding of [D-Tyr-Gly]A-71378 was best fitted by a two-site model. In contrast, 125I-gastrin binding was fitted with a single-site model. For inhibiting binding of 125I-[D-Tyr-Gly]A-71378, the CCK antagonists had relative affinities of L-364,718 >> L-365,260, and the reverse was true with 125I-gastrin. Correlation of binding with changes in biological activity suggested low-affinity CCK-A-R were mediating these changes. These results demonstrate directly for the first time that guinea pig chief cells possess CCK-A-R and CCK-B-R. The pharmacology of these CCK-A-R resembles those on other tissues. This novel, highly selective CCK-A ligand should be useful because it will identify CCK-A-R when they make up as little as 0.2% of the total CCK receptor number.

Topics: Animals; Benzodiazepinones; Devazepide; Gastric Mucosa; Gastrins; Guinea Pigs; Ligands; Male; Oligopeptides; Pancreas; Pepsinogens; Phenylurea Compounds; Receptors, Cholecystokinin; Sincalide; Stomach

Peptide alpha amidation is required to produce some hormones, such as gastrin, from their glycine-extended precursors. This terminal posttranslational processing reaction is thought to be essential for the biological activation of many peptide hormones; only amidated gastrin exerts a physiological effect that results in gastric acid secretion. However, both amidated gastrin and glycine-extended gastrin stimulate proliferation of exocrine pancreatic cell line AR4-2J through selective receptors for the substrate and the product, respectively, of peptide alpha amidation. Thus, the amidation reaction may function as a determinant of the specific biological actions of products derived from prohormones.

Topics: Benzodiazepinones; Binding Sites; Cell Division; Gastrins; Humans; Indoles; Meglumine; Octreotide; Ornithine Decarboxylase; Phenylurea Compounds; Receptors, Cholecystokinin; Tumor Cells, Cultured

With the availability of selective gastrin/CCKB (L365,260) and CCKA (L364,718) receptor antagonists the present study was designed to investigate the role of gastrin and cholecystokinin (CCK) receptors in meal-stimulated gastric acid secretion. Gastric acid output was measured by continuous intragastric titration in conscious rats. Vehicle (dimethylsulfoxide/saline, 3:1), L365,260 (3 or 9 mg/kg), or L364,718 (1 mg/kg) was given by i.v. bolus injection. Basal acid output was strongly inhibited by both doses of L365,260 while L364,718 had no effect. Intragastric peptone (4%, w/v) increased acid secretion 40-65% of the response to a maximal dose (2.5 nmol/kg per h) of gastrin-17. L365,260 completely abolished gastrin-17 stimulated acid secretion and partially inhibited peptone-induced acid secretion. Blockade of CCKA receptors by L364,718 did not affect peptone-stimulated acid output. This study demonstrates that gastrin/CCKB receptors are important in regulating basal acid secretion in the conscious rat while CCKA receptors do not appear to influence basal or peptone-stimulated gastric acid secretion. Blockade of gastrin/CCKB receptors partially inhibits intragastric meal-stimulated acid secretion indicating that the gastrin/CCKB receptor has a physiological role as mediator of food-stimulated acid secretory response in conscious rats.

Topics: Animals; Benzodiazepinones; Cholecystokinin; Devazepide; Eating; Gastric Acid; Gastrins; Hormones; Injections, Intravenous; Male; Peptones; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptors, Cholecystokinin

In this investigation we studied the influence of two gastrin fragments, pentagastrin and nonsulfated heptadecagastrin, and two cholecystokinin fragments, sulfated and desulfated cholecystokinin 26-33, on intracellular and secreted triacylglycerol in isolated hepatocyte cultures. Both gastrin fragments inhibited triacylglycerol release in a biphasic manner, exhibiting maximal effect at 0.1 nmol/L (nonsulfated heptadecagastrin) and 0.3 nmol/L (pentagastrin). At these concentrations triacylglycerol secretion was 42% (nonsulfated heptadecagastrin, p < 0.001) and 62% (pentagastrin, p < 0.001) lower than in cells untreated with gastrin. Sulfated cholecystokinin 26-33 caused a 35% decrease in triacylglycerol secretion at 0.1 nmol/L (p < 0.01), and desulfated cholecystokinin 26-33 caused a 53% decrease at 0.2 nmol/L (p < 0.001). In all experiments, the hormone-induced decrease in triacylglycerol secretion was accompanied by an increase in intracellular triacylglycerol content. The cholecystokinin-A receptor antagonist L-364, 718 did not affect the decrease in triacylglycerol secretion induced by 0.3 nmol/L pentagastrin, whereas the cholecystokinin-B receptor antagonist L-365, 260 inhibited the pentagastrin effect at concentrations above 50 nmol/L. These results suggest that gastrin, cholecystokinin or some other gastrinlike hormone (or all three) may play a previously unrecognized regulatory role with respect to hepatic very low density lipoprotein secretion.

Topics: Animals; Benzodiazepinones; Cells, Cultured; Depression, Chemical; Devazepide; Gastrins; Liver; Male; Pentagastrin; Peptide Fragments; Phenylurea Compounds; Rats; Rats, Sprague-Dawley; Receptors, Cholecystokinin; Sincalide; Triglycerides

The ability of gastrin, histamine, and carbachol to stimulate acid secretion by direct action on gastric parietal cells is well established but the role of intracellular Ca2+ concentration ([Ca2+]i) in mediating these effects is the subject of some controversy. To examine this issue further, secretagogue-mediated changes in [Ca2+]i in single isolated canine gastric parietal cells were examined by microspectrofluorometry of fura-2-loaded cells. Resting [Ca2+]i in single parietal cells was 63 +/- 6 (SE) nM. Carbachol, 10(-5) M, induced a maximum elevation in [Ca2+]i with an initial transient rise of 178 +/- 24 (SE) nM, which was maintained in the absence of extracellular Ca2+ and a sustained plateau of 112 +/- 20 (SE) nM, which was abolished by removal of extracellular Ca2+. Both effects were reversed by the muscarinic receptor antagonist atropine. Gastrin (10(-9)-10(-7) M) also induced a bimodal rise in [Ca2+]i with a maximal initial transient rise of 206 +/- 14 nM and a sustained plateau of 94 +/- 9 nM. Both components of the [Ca2+]i response to gastrin were reversed by the gastrin specific antagonist L 365260. Lower concentrations of gastrin (10(-10) M) induced repetitive transient increases (oscillations) in cytosolic Ca2+. The amplitude of the first spike was less than 50% of the transient rise in [Ca2+]i stimulated by 10(-8) M gastrin. The oscillations occurred at a rate of 0.9/min, gradually decreasing in amplitude within 15 min of secretagogue administration. Histamine (10(-4) M) led to a minimal rise in [Ca2+]i (less than 5% of control) in less than 10% of the canine parietal cells tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Benzodiazepinones; Calcium; Carbachol; Cytosol; Dogs; Dose-Response Relationship, Drug; Gastrins; Histamine; In Vitro Techniques; Kinetics; Parietal Cells, Gastric; Phenylurea Compounds; Rabbits; Signal Transduction; Species Specificity; Spectrometry, Fluorescence