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)

The effects of the recognized diabetogenic hormones, growth hormone and ACTH, administered in vivo, on (pro-)insulin biosynthesis and secretion in isolated islets of normal rats were studied. Rats were treated with these hormones for 4 weeks. Afterwards, their collagenase-isolated islets were incubated with [3H]leucine for 3 h. (Pro-)Insulin biosynthesis was estimated for the incorporation data into islet protein fractions. Islets of treated rats released significantly more insulin and incorporated significantly less [3H]leucine into proinsulin and insulin compared with controls when tested at 100 mg glucose/100 ml. At 200 mg glucose/100 ml, no significant differences were found. The findings demonstrate an impact of these hormones on the B-cells derived from normal pancreas of intact rats. The alterations are, however, not very pronounced and can be easily compensated under a strong glucose stimulus. It appears that the mechanisms for (pro-)insulin biosynthesis and release in rats are more resistant against the diabetogenic actions of pituitary hormones than in other species.
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PMID:Hypophysis and function of pancreatic islets. IV. Effect of treatment with growth hormone and corticotrophin on insulin secretion and biosynthesis in isolated pancreatic islets of normal rats. 20 46

To study the influence of insulin on its own secretion, collagenase-isolated islets of rat pancreas were prelabelled with [3H]leucine for 2 h. After washing the islets, (pro-)insulin release was stimulated by glucose in the presence or absence of exogenous insulin (up to 2-5 mu./ml). Hormone release was unchanged by the presence of exogenous insulin as judged by determination of both immunoreactive insulin and radioactivity incorporated into the proinsulin and insulin fractions of the medium. No direct feedback mechanism for insulin secretion was apparent from this study.
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PMID:Release of immunoreactive and radioactively prelabelled endogenous (pro)-insulin from isolated islets of rat pancreas in the presence of exogenous insulin. 33 Jul 86

Dispersed cell preparations enriched in beta-cells were obtained by collagenase digestion of fetal bovine pancreas and separation by Ficoll gradient centrifugation. These cells actively incorporated [3H]leucine into proinsulin and insulin. Incubation of these cells in the presence of the arginine analogue, L-canavanine, resulted in the inhibition of conversion of newly formed proinsulin to insulin and the appearance of a radioactive component of molecular weight 11,000-12,000. Incorporation of [35S]methionine into this component was detected in the presence of canavanine, an event not observed in control incubation. Canavanine thus induced the formation of a component possessing molecular weight and compositional properties expected for preproinsulin. Further characterization of cellular products by polyacrylamide slab gel electrophoresis in sodium dodecyl sulfate showed a highly labeled band corresponding to molecular weight 18,000-20,000 which might be involved in insulin biosynthesis.
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PMID:Preparation of beta-cells from fetal bovine pancreas: characterization of insulin biosynthetic activity. 38 31

The biosynthetic activity of the B-cells of obese hyperglycemic mice (obob) was measured by the incorporation of [3H]leucine into proteins in collagenase-isolated pancreatic islets. To quantitate the incorporation into proinsulin and insulin, an immune binding method was used. For this purpose, anti-insulin serum was coupled to cyanogen bromide-activated SepharoseR 4B. This turned out to be a specific and versatile technique for the measurement of newly synthesized proinsulin and insulin in the B-cells. The B-cells of obob mice appear to be well adapted to a high rate of hormone biosynthesis, since at 16.7 mM glucose 44% of [3H]leucine incorporated into TCA-precipitable proteins was bound to the insulin antibodies coupled to Sepharose 4B. The insulin biosynthetic rate was stimulated 9 times at 16.7 mM glucose, during a 3-h incubation, compared with the basal insulin biosynthesis rate.
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PMID:Anti-insulin serum coupled to Sepharose 4B as a tool for the investigation of insulin biosynthesis in the B-cells of obese hyperglycemic mice. 110 96

Insulin secretion in response to glucose, glucose-stimulated insulin biosynthesis and insulin content was studied in pancreatic islets freshly isolated from male Wistar rats (150-200 g) with galactosamine-induced hepatitis. Animals were sacrificed by decapitation 3, 6, 12 and 24 hours after a single intraperitoneal injection of 500 mg/kg of galactosamine. Isolated islets prepared by collagenase method were perifused in Swim's medium with 20 mM glucose at 37 degrees C up to 30 minutes. Samples were taken at 2-10 min intervals for insulin assay. Insulin biosynthesis was assessed by the incorporation of [3H]-leucine into immunoprecipitable products (insulin and proinsulin) in pancreatic islets after 120 min incubation with 20 mM glucose. Glucose-stimulated insulin secretion was significantly increased at 6, 12 and 24 hours following the administration of galactosamine compared to control. The rate of insulin biosynthesis was stimulated to 170, 138 and 185% of control level 3, 6 and 12 hours after galactosamine-treatment, respectively. Significant increase in insulin content of islets was found 24 hours after galactosamine treatment, following the increased insulin biosynthesis. The present results indicate that pancreatic B cell function is activated in early stage of acute liver injury.
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PMID:Increase in glucose-stimulated insulin release and insulin biosynthesis in isolated pancreatic islets from D-galactosamine-treated rats. 219 63

The ability of the pancreatic beta-cell to repair itself after a cytotoxic injury and reassume its functional activities may be a key issue in affording protection from insulin-dependent diabetes mellitus. The molecular mechanisms behind the functional responses of the beta-cell after cytotoxic damage are still largely unknown. The present study in an attempt to elucidate this issue. Mouse pancreatic islets were isolated with collagenase and, after overnight culture, exposed for 30 min at 37 C to 2.2 mM streptozotocin (SZ) or vehicle alone (controls). The islets were subsequently cultured for 6 days in medium RPMI-1640 plus 10% calf serum. After the culture they were subjected to light microscopical examinations or different functional tests during short term incubations. The SZ-treated islets showed markedly diminished insulin release after stimulation with the beta-cell nutrients glucose and leucine plus glutamine. Compounds known to increase intracellular cAMP [theophylline and (Bu)2-cAMP] were able to partially counteract the SZ-induced reduction of insulin release. Stimulation with arginine could also slightly restore the impaired insulin release. Glucose-stimulated oxygen uptake, proinsulin biosynthesis, and insulin and insulin mRNA contents were also decreased, with values at about 50% of the controls. However, the cellular contents of DNA and RNA and total protein biosynthesis rates were essentially normal. Besides mild degranulation in some islets, the morphological appearance of the SZ-treated islets did not reveal any obvious differences compared to the control islets. The present observations suggest that after a toxic injury there remains a population of partially damaged beta-cells, which are able to maintain most of their basal metabolic functions, but fail to maintain adequate insulin biosynthesis and release.
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PMID:Preferential reduction of insulin production in mouse pancreatic islets maintained in culture after streptozotocin exposure. 245 14

Several lines of evidence suggest that autoimmune processes are involved in the pathogenesis of Type I diabetes mellitus. Monocyte-macrophages are among the first mononuclear cells to invade the islets of Langerhans in various murine diabetic syndromes, and blockade of monocyte-macrophage functions by injection of silica particles in these animals prevents the development of the disease. Monokines such as interleukin 1 (IL-1) are known to mediate tissue lesions by inducing collagenase and prostaglandin E2 (PGE2) production. In addition, IL-1 has been demonstrated to inhibit proinsulin biosynthesis and secretion in pancreatic islet cells. Using 3-d cultured rat islets we have found that (a) the lowering of insulin release induced by human recombinant IL-1 (rIL-1) is dose-dependent with a decrease to 21% of control value at the higher rIL-1 tested concentration (500 pg/ml), and about two times more pronounced than the decrease in cellular insulin content, which reached 44% of control value at the highest rIL-1 concentration; (b) rIL-1 stimulates islets to secrete PGE2 but the addition of indomethacin, which blocks PGE2 production, does not affect the decrease in insulin release and content caused by IL-1, suggesting a limited role of endogenous PGE2 as a mediator in this system; and (c) a specific, noncytotoxic IL-1 inhibitor, shown in other cell systems to block the binding of IL-1 to its receptor, prevents the rIL-1 lowering of insulin content and minimizes the decrease of insulin release.
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PMID:A natural interleukin 1 (IL-1) inhibitor counteracts the inhibitory effect of IL-1 on insulin production in cultured rat pancreatic islets. 252 7

Studies of the biological activity of proinsulin have resulted in widely varying conclusions. Relative to insulin, the biological activity of proinsulin has been reported from less than 1% to almost 20%. Many of the assays in vitro for the biological potency of proinsulin have utilized isolated rat adipocytes. To examine further the interaction of proinsulin with rat adipocytes, we prepared specifically-labelled proinsulin isomers that were iodinated on tyrosine residues corresponding to the A14, A19, B16 or B26 residue of insulin. These were incubated with rat adipocytes and their metabolism was examined by trichloroacetic acid precipitation, by Sephadex G-50 chromatography, and by h.p.l.c. chromatography. By trichloroacetic acid-precipitation assay, there was little or no proinsulin degradation. By G-50 chromatography and subsequent h.p.l.c. analysis, however, we found that the labelled proinsulin isomers were converted rapidly and almost completely to materials which eluted differently on h.p.l.c. from intact proinsulin. This conversion was due primarily to proteolytic activity which adsorbed to the fat cells from the crude collagenase used to isolate the cells. Two primary conversion intermediates were found: one with a cleavage at residues 23-24 of proinsulin (the B-chain region of insulin), and one at residues 55-56 in the connecting peptide region. These intermediates had receptor binding properties equivalent to or less than intact proinsulin. These findings show that isolated fat cells can degrade proinsulin to intermediates due to their contamination with proteolytic activity from the collagenase used in their preparation. Thus the previously reported range in biological activities of proinsulin in fat cells may have arisen from such protease contamination. Finally, the present findings demonstrate that a sensitive assay for degradation of hormones is required to examine biological activities in isolated cells.
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PMID:Conversion of biosynthetic human proinsulin to partially cleaved intermediates by collagenase proteinases adsorbed to isolated rat adipocytes. 284 5

Insulin has been reported to degrade inside the islets and islet lysosomal proteases have been thought to take part. As chloroquine is regarded as a potent lysosomotropic agent, an attempt has been made to see whether chloroquine has an influence on intrainsular degradation of insulin. After preculture of collagenase-isolated rat islets at 11 mM glucose together with [3H]leucine for 3 days for labelling newly synthesized insulin, islets were cultured for 1 day at 2.2 or 22 mM glucose with or without 0.02 mM chloroquine. Afterwards, radioactivity was measured in the proinsulin/insulin fraction. For control, the influence of chloroquine during 3-h incubation of both freshly isolated and precultured islets was also studied. During the 1-day culture at 2.2 mM glucose, prelabelled insulin was degraded significantly and addition of chloroquine did not alter the amount of insulin degraded. At 22 mM glucose, no significant amount of insulin had been degraded. During the 3-h incubation of freshly isolated as well as precultured islets, chloroquine was found to inhibit significantly glucose-induced biosynthesis of insulin. Glucose-induced release of insulin, however, was not influenced by chloroquine. It is concluded that chloroquine does not influence glucose-induced release or intra-insular degradation of insulin, but it interferes with the biosynthesis of insulin.
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PMID:Effect of chloroquine on biosynthesis, release and degradation of insulin in isolated islets of rat pancreas. 304 45

The ovarian granulosa cell has recently been shown to be a site of somatomedin-C/insulin-like growth factor I (Sm-C/IGF-I) production, reception, and action. These observations have generally been interpreted to suggest the existence of an autocrine loop concerned with granulosa cell physiology. It is the objective of the in vitro studies reported herein to extend these observations by evaluating the interaction of Sm-C/IGF-I with the adjacent thecal-interstitial cell. Treatment of collagenase-processed whole ovarian dispersates or highly enriched (greater than 90%) thecal-interstitial cells from immature rats with Sm-C/IGF-I (50 ng/ml) or hCG (1 ng/ml), resulted in 2.1- and 4.0-fold increments in the accumulation of androsterone (3 alpha-hydroxy-5 alpha-androstane-17-one), the main androgenic steroid identified in culture media. However, combined treatment with both agents unmasked a synergistic interaction producing a 3.3-fold increase in the hCG-stimulated accumulation of androsterone, an effect consequent to enhanced androgen biosynthesis rather than diminished degradation. Unaccounted for by an increase in viable ovarian cell numbers and independent of the hCG dose (0.1-10 ng/ml) used, the Sm-C/IGF-I effect proved time and dose dependent, with a projected minimal effective dose of 3 ng/ml and a minimal time requirement of 72 h. [125I]Iodo-Sm-C/IGF-I binding to untreated highly enriched thecal-interstitial cells proved saturable, with a single class (Hill coefficient = 0.98 +/- 0.01) of high affinity (Kd = 3.0 nM), low capacity (maximum binding = 10,840 +/- 2,108 sites/cell) binding sites. Limited specificity studies using related peptides produced a rank order of competitive potency of: Sm-C/IGF-I greater than multiplication stimulating activity greater than insulin, a pattern compatible with the presence of type I IGF receptors. Other related peptides, such as porcine proinsulin and porcine desoctapeptide insulin, proved weakly effective in inhibiting Sm-C/IGF-I binding to its receptor; unrelated peptides such as porcine relaxin and erythropoietin were without effect. Taken together, these findings suggest that 1) the thecal-interstitial cell, like the granulosa cell, may be a site of Sm-C/IGF-I reception and action, and 2) the ability of high dose insulin to stimulate ovarian androgen biosynthesis may be due to its capacity to act as a Sm-C/IGF-I surrogate, its high dose requirements reflecting cross-interaction with the type I receptor.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Somatomedin-C/insulin-like growth factor I as an enhancer of androgen biosynthesis by cultured rat ovarian cells. 327 92


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