Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cytoplasmic Ca2+ is regarded as an intracellular messenger for acetylcholine- and cholecystokinin (CCK)-stimulated pancreatic enzyme secretion. We investigated in the in vitro model of isolated rat pancreatic acini whether or not Ca2+-channel blockers are able to inhibit Ca2+-mediated enzyme secretion. Isolated rat pancreatic acini were prepared via collagenase digestion. The effect of various Ca2+-channel blockers on amylase secretion stimulated by various secretagogues was monitored. Verapamil, but not nitrendipine, dose-dependently reduced CCK8- and carbachol-stimulated enzyme secretion. Higher doses of either CCK8 or carbachol could not reverse the inhibition caused by verapamil. Amylase secretion stimulated by the ionophore A23817 was not altered by verapamil. Verapamil augmented enzyme secretion stimulated by secretagogues which work through cAMP as second messenger. 3H-N-methylscopolamine- and 125I-Bolton-Hunter-CCK8-binding to pancreatic acini was dose-dependently inhibited by verapamil, but the inhibition curves did not parallel the inhibition curves with unlabeled receptor agonists. Thus, the impairment of exocrine pancreatic amylase secretion by verapamil is probably not due to its known "Ca2+-channel" blocking abilities in other tissues but is rather caused by noncompetitive effects on the level of muscarinic receptors and receptors for CCK.
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PMID:Influence of "calcium2+-channel blockers" on exocrine pancreatic secretion by isolated rat acini. 246 43

The inhibitory effects of CR-1409, a new glutaramic acid derivative developed as a cholecystokinin (CCK) receptor antagonist, on caerulein-stimulated amylase secretion and on intracellular Ca2+ ([Ca2+]i) mobilization were studied in isolated rat pancreatic acini. Pancreatic acini were prepared by collagenase digestion method and loaded with 1 microM fura-2/AM for measurement of the intracellular free Ca2+ concentration. Amylase release was examined by a perifusion method. Stimulation with 10(-10) M caerulein, 10(-5) M carbachol, or 10(-8) M gastrin-releasing peptide (GRP) led to biphasic amylase release and increase in [Ca2+]i. CR-1409 at 1 and 5 microM inhibited, by 50 and 84%, respectively, the amylase secretion and increase in [Ca2+]i induced by 10(-10) M caerulein, and 25 microM CR-1409 completely inhibited both amylase secretion and increase in [Ca2+]i induced by caerulein. However, 25 microM CR-1409 did not inhibit unstimulated secretion of amylase or the secretions induced by carbachol and GRP, which are also mediated by changes in intracellular Ca2+. We conclude that CR-1409 acts as a specific inhibitor of the CCK receptor in the pancreas, and is useful in studies on the involvement of the release and action of CCK in vitro.
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PMID:The inhibitory effect of CR-1409 on amylase secretion and intracellular Ca2+ mobilization in rat pancreatic acini in vitro. 248 Oct 56

Thyroid hormones influence Ca2+ homeostasis in both skeletal and cardiac muscle. Since secretory cells, like muscle cells, store and use Ca2+ in stimulus-response coupling, we have studied the effects of thyroid status on Ca2+ mobilization and secretion in a model secretory tissue, the pancreatic acinar cell. Hyperthyroidism was induced by rats by daily, subcutaneous injections of triiodothyronine for 8 days and hypothyroidism by adding 6-n-propyl-2-thiouracil to the drinking water for 14 days. Pancreatic acini were prepared by collagenase digestion of pancreatic tissue from hyper- and hypo-thyroid animals and from euthyroid controls. Ca2(+)-mobilization was assessed using Quin-2 fluorescence and secretion by assaying amylase release. The data indicate that the amount of Ca2+ mobilized by the muscarinic agonist carbachol or by cholecystokinin octapeptide increases with increasing thyroid hormone concentrations. Only in hypothyroidism was this change in Ca2+ homeostasis reflected by a parallel change in amylase secretion. This implies the existence of some compensatory mechanism which stabilizes secretory rate in the face of stimulus-evoked increases in intracellular Ca2+ concentration.
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PMID:Influence of thyroid status on Ca2+ mobilization and amylase secretion in rat pancreatic acini. 248 94

Rat gastric mucosal cells were isolated with the aid of 0.1% collagenase and Dispase. Pepsinogen secretion from these cells was stimulated by carbachol, cholecystokinin octapeptide (CCK(S)-8) and pentagastrin, but not by histamine. Attempts to obtain a sufficient number of cells using a higher concentration of Dispase resulted in disappearance of the responses to secretagogues. However, when gastric mucosal cells thus prepared were cultured for 24 h in a CO2 incubator, they were found to respond not only to carbachol, CCK(S)-8 and pentagastrin, but also to histamine, resulting in an increase in pepsinogen secretion. The secretagogue-induced pepsinogen secretion was inhibited by its antagonist in a dose-dependent manner. These results suggest that the receptor present in chief cells for pepsinogen secretion was destroyed during the isolation procedure and regenerated during culture.
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PMID:Pepsinogen secretion from cultured rat gastric mucosal cells. 259 21

To determine the nature of the pancreatic islet cell cholecystokinin (CCK) receptor, we studied CCK receptor binding and biologic activity in isolated rat pancreatic islets. Binding of 70 pM 125I-CCK to collagenase-prepared isolated rat pancreatic islets at 24 degrees C was one-half maximal after 5 min and maximal at 60 min. At 60 min, specific binding was 12% of total radioactivity per 100 micrograms islet protein; nonspecific binding (in the presence of 1 microM CCK 8) was less than 2% of total radioactivity. Unlabeled CCK 33 inhibited labeled hormone binding one-half maximally at 2 nM; Scatchard analysis showed one binding site (Kd, 2.3 +/- 0.4 nM; Bmax, 8.1 pmol/mg protein). The agonist selectivity of this binding site was: CCK 8 = CCK 33 greater than desulfated-CCK 8 greater than CCK 4. Two CCK antagonists were studied; N-carbobenzoxy-L-tryptophan was more potent than dibutyryl-cGMP. When the effect of CCK on insulin release from the islets was studied, the order of potency of CCK agonists and antagonists on insulin secretion was the same as the order of their ability to inhibit 125I-CCK binding. The effect of CCK on insulin secretion was dependent on the glucose concentration in the media. CCK had no effect at 5.6 mM glucose and was fully effective at 11.0 mM glucose. These data, therefore, indicate that: specific binding sites for CCK are present in rat pancreatic beta cells; and CCK acts in concert with glucose to stimulate insulin secretion.
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PMID:Evidence that cholecystokinin interacts with specific receptors and regulates insulin release in isolated rat islets of Langerhans. 300 Aug 56

The question of whether the Ca2+ ionophore A23187 affects collagen production relative to total protein synthesis or has possible effects on collagen degradation was investigated. Cultured normal human fibroblasts were incubated with radioactive proline, and the radioactivity of collagenase-sensitive and -resistant proteins was used to calculate the rates of protein production. The net production of collagen relative to total proteins was inhibited by A23187 in a dose-related manner, and 50% inhibition of basal collagen production was achieved with 0.6 microM A23187. There was a 70% decrease in the absolute rate of collagen production in the presence of 0.6 microM A23187 which represented a 4-fold greater inhibition of collagen production than of noncollagen protein production. The major mechanism for the decreased net production of collagen was decreased synthesis, rather than increased degradation. Ca2+ mobilization induced by cholecystokinin octapeptide was also associated with selective inhibition of collagen production in normal human fibroblasts. These studies establish that the Ca2+ ionophore A23187 induces a selective decrease in collagen polypeptide synthesis by normal human fibroblasts and suggest a modulatory role of Ca2+ on collagen metabolism.
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PMID:Selective inhibition of collagen synthesis by the Ca2+ ionophore A23187 in cultured human fibroblasts. 309 97

Calcitonin is known to inhibit secretion of gastrin and insulin in vivo. The objective of this study was to determine whether calcitonin can act directly on pancreatic islets in vitro to inhibit insulin release. Isolated islets were obtained from collagenase-treated rat pancreas, and three peptides (gastrin-releasing peptide, cholecystokinin-8, bombesin) and glucose were used to stimulate insulin release. All agents caused a significant increase in insulin secretion and calcitonin inhibited these responses, but had no consistent effect on basal release. This study provides evidence that calcitonin is an effective inhibitor of insulin secretion and acts directly on islet tissue.
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PMID:Calcitonin inhibition of insulin release from isolated rat pancreatic islets. 351 Jan 39

Preincubation of collagenase-isolated rat islets for 150 min with 100 U/ml purified human interleukin 1 (IL-1) altered their ability to secrete insulin. Whereas basal release rates with 4 mM glucose were comparable in control and IL-1-treated islets, both the first and second phases of release in response to 20 mM glucose were significantly reduced from IL-1-treated tissue. IL-1 pretreatment also impaired the secretory response to the combination of 100 nM cholecystokinin plus 7 mM glucose. However, the secretory response to 10 mM alpha-ketoisocaproate was comparable in control and IL-1-pretreated islets. Reducing the IL-1 exposure time to 60 min was accompanied by an augmented first phase of release to 20 mM glucose. Second phase secretion was diminished. The use of glucose measured after the perifusion was similar in control and IL-1-treated islets. Similar to other compounds that adversely impact on beta-cell viability, the inhibitory effect of IL-1 on release may presage a cytotoxic action of monokine.
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PMID:Interleukin 1 inhibits insulin secretion from isolated perifused rat islets. 353 Aug 42

A superfusion technique was developed as a model system for the study of stimulus-secretion coupling in collagenase-dispersed rat pancreatic acinar cells. Cells (10(7)) were combined with a slurry of Biogel P-4 beads and the mixture was decanted into a plastic column (1.5 cm X 8.5 cm) and perfused with Krebs-Ringer. Amylase activity was determined in sequentially collected effusate fractions and used to estimate the secretory rate. Carbachol, carbachol plus dibutyryl cyclic AMP, cholecystokinin-pancreozymin, and the ionophore A-23187 all stimulated a rapid increase in the rate of secretion. Cell integrity was unaffected by these stimulants as evidenced microscopically and by the lack of lactate dehydrogenase activity in the effusates. Enzymes secreted in response to secretagogues were collected, concentrated, and isoelectrofocused on polyacrylamide gels. A film detection technique was developed to localize amylase activity. The model system has the following advantages: (1) secreted proteolytic products are removed from the vicinity of cells, thereby preventing direct cellular damage and hydrolysis of peptide agonist; (2) the need to add trypsin inhibitors is eliminated and only a minimal addition of albumin (0.001%) is required, thus allowing the separation and distortion-free analysis of secreted proteins; (3) the perfusion conditions can be changed rapidly without disturbing the cells. The model described is therefore well suited to the study of both molecular and kinetic events involved in the enzyme secretory phenomenon in exocrine pancreas.
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PMID:A model system for the study of stimulus - enzyme secretion coupling in rat pancreatic acinar cells. 616 55

Isolated smooth muscle cells were prepared from the fundus of guinea pig stomach by incubation with collagenase. Incubating the cells with the C-terminal octapeptide of cholecystokinin induced contraction, which was measured by micrometry and expressed as percent decrease in mean cell length. Cholecystokinin-induced contraction was maximal within 30 s and reduced cell length by approximately 37%. The threshold concentration of cholecystokinin was 0.1 pM, and the maximally effective concentration was 0.3 nM. Contraction caused by cholecystokinin could be inhibited by proglumide and by glucagon. Inhibition by proglumide was competitive and resulted in a parallel rightward shift of the cholecystokinin dose-response curve. In contrast, inhibition by glucagon was noncompetitive and resulted in a reduction in the efficacy of cholecystokinin without a change in its potency. Furthermore, proglumide-induced inhibition was specific for cholecystokinin, whereas glucagon-induced inhibition of contraction was nonspecific and reduced the contraction caused by carbamylcholine and the calcium ionophore A23187.
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PMID:Cholecystokinin-induced contraction of dispersed smooth muscle cells. 629 16


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