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 effect of glucose on acute 45Ca uptake and efflux in collagenase-isolated islets was studied using a double-isotope incubation technique with [3H]sucrose as an extracellular marker. Both 45Ca uptake (0-70 min) and efflux (0-80 min) were measured in either 3 or 20 mM glucose. Calcium-45 uptake and efflux were biphasic demonstrating a rapid phase (0-1 min) followed by a slow phase. Glucose (20 mM) increased the rate constant for slow-phase 45Ca uptake 7-fold and had no effect on the rapid phase. Suppression of insulin release by D2O (100%) did not affect glucose-induced 45Ca uptake indicating that this increased uptake occurred independent of insulin release. Rapid-phase and slow-phase 45Ca efflux rate constants were unaltered by 20 mM glucose and inhibition of insulin release by D2O did not influence 45Ca efflux. The rapid-phase movement of 45Ca may represent a rapidly exchangeable calcium pool at the cell membrane whereas the slow phase may be transmembranous calcium movement, as has been reported for calcium transport in HeLa and kidney cells.
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PMID:The effect of glucose on the acute uptake and efflux of calcium-45 in isolated rat islets. 33 Jan 51

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

In this work we have investigated the effect of serotonin on glucagon release in mouse pancreatic islets isolated by the collagenase technique. Incubation of the islets with serotonin (4 X10(-3)mol/l) was associated with an inhibition of glucagon output both in the basal medium (3.3 mmol/l glucose) and in the presence of arginine (10 mmol/l). The inhibitory effect of serotonin on basal glucagon release was also apparent at concentrations of 2 X10(-3) mol/l, 10(-3)mol/l and 5 X 10(-4) mol/l. Addition of 5-hydroxytrypophan (4 X10(-3) mol/l) to the incubation medium was without effect on basal glucagon output while it significantly reduced arginine-induced glucagon release. In contrast, tryptophan (4 X10(-3) mol/l) provoked glucagon secretion. As inferred from our previous human studies, the present data indicate that serotonin is able to inhibit glucagon secretion. These findings provide further support for the participation of a serotoninergic mechanism in the control of A-cell function.
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PMID:Inhibition of glucagon release by serotonin in mouse pancreatic islets. 33 6

Forty-nine dogs were made diabetic by total pancreatectomy. Fifteen untreated pancreatectomized animals survived a mean (+/-S.E.) of 7.0 +/- 1.1 days with a mean (+/-S.E.) plasma glucose level of 402 +/- 26 mg/100 ml before death. The pancreata of 32 dogs were distended with cold (4 degrees ) Hanks' solution, minced, digested with collagenase (600 U/ml tissue) for 15-25 minutes, and autotransplanted either into the splenic artery (three dogs), directly into the splenic pulp (21 dogs), or into the portal vein (ten dogs). Tissue infusion into the splenic artery resulted in infarction and persistent hyperglycemia. Direct implantation into the splenic pulp of tissue digested for 15, 20 and 25 minutes resulted in permanent normoglycemia (fasting plasma glucose < 150 mg/100 ml) in 7 of 8, 7 of 7, and 6 of 6 dogs respectively. Glucose tolerance test mean (+/-S.E.) K values (% decline of plasma glucose concentration/minute) in these groups two weeks after transplantation were 1.20 +/- 0.20%, 1.60 +/- 0.25 and 0.70 0.08% respectively, indicating that 20 minutes digestion was best for intrasplenic transplantation. Tissue prepared in the optimal manner (20 minutes digestion) and embolized into the liver resulted in normoglycemia in three of eight dogs, and a mean (+/-S.E.) K value of 0.77 +/- 0.10%. Both dogs receiving tissue dispersed for 25 minutes into the portal vein remained hyperglycemic. In the dogs subjected to intraportal transplantation, portal pressure rose from a mean (+/-S.E.) of 6.5 +/- 0.6 cm H(2)O before to 21.9 +/- 2.2 cm H(2)O immediately after tissue embolization, but declined to 6.5 +/- 1.0 cm H(2)O by ten weeks in animals becoming normoglycemic. We conclude that in dogs direct implantation of pancreatic tissue into the splenic pulp is superior to embolization into the portal vein or splenic artery because the splenic circulation is not compromized, portal hypertension is obviated, and glucose metabolism is best controlled as judged by glucose tolerance test K values.
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PMID:Autotransplantation of pancreatic fragments to the portal vein and spleen of totally pancreatectomized dogs: a comparative evaluation. 33 53

A procedure was developed for the isolation of intact islets of Langerhans from sheep pancreas. The pancreas was disrupted by syringe injection of Hanks solution followed by collagenase incubation and islet separation by sedimentation. The islets were incubated in varying concentrations of glucose and butyrate. The rate of insulin release was approximately linear while the glucose and butyrate concentrations were increased. In additional studies at 2.5 and 5.0 mM levels of substrate concentration, the stimulation of insulin had the following pattern: octanoate greater than hexanoate greater than butyrate, whereas beta-hydroxybutyrate, lactate, acetate, and propionate had only slight stimulatory effects that were not statistically significant. Decanoate did not alter insulin release from isolated islets. These data confirm earlier in vivo reports that fatty acids stimulate pancreatic hormone release in sheep and that the stimulus is related to chain length of the fatty acid through C-8 but that C-10 has no effect. A hypothesis was suggested to explain these results based on chain length, solubility, and plasma membrane alterations.
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PMID:Effect of fatty acids on isolated ovine pancreatic islets. 34 24

3[H]-Leucine incorporation into (pro)insulin and insulin secretion was investigated using islets prepared by collagenase digestion from pancreata of rats pretreated with the cholimimetic agent pilocarpine or with saline (controls). Under the influence of pilocarpine pretreatment the [3H]-leucine incorporation into islet proteins with insulin immunoreactivity is enhanced at 6 mM glucose in the incubation medium of the islets but the incorporated radioactivity at 18 mM glucose is independent of the pretreatment of the animals. Only small or no changes were found regarding insulin secretion. It is concluded that an influence of pilocarpine pretreatment should be taken into consideration using such islets for studies on the regulation of (pro)insulin biosynthesis.
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PMID:Influence of pilocarpine pretreatment on (pro)insulin biosynthesis of isolated islets of rats. 35 84

In the present work, homogeneous isolated pancreatic islet-cells were transplanted to diabetic rats with the aim of verifying if the transplanted tissue could survive and reduce the plasma glucose concentration on the alloxan-induced diabetic receptors. For the isolation of the pancreatic islets, pancreas was incubated in collagenase solution for about 13 +/- 3 minutes, followed by centrifugation in Ficoll gradients. The islets, 3 000 to 5 000, were transplanted to alloxan diabetic recipients, in a territory, preferentially with portal-hepatic drainage (mesentery and spleen). Sixty per cent of the recipients exhibited a fall of the plasma glucose concentration, up to 70%, while in the control animals, the diabetes persisted. The islets were found in the recipients mesentery up to 10 days after transplantation, and all of them showed heavily granulated (aldehyde fuchsin positive) beta cells. After this time, islets were not found. These results indicate that islets can survive and attenuate diabetes in alloxan-treated rats, and that, probably, the number of islets transplanted as well as the receiving areas play an important role.
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PMID:Transplantation of islets of Langerhans in diabetic rats. 35 20

Kinetics of (45)Ca efflux and insulin release were studied in collagenase-isolated rat islets during 2-h perifusions with calcium-depleted (0.05 mM) bicarbonate-phosphate buffer containing 2.2 mM glucose. Addition of glucose (16.7 mM) suppressed (45)Ca efflux by 30%. Removal of glucose caused an "off response" of insulin release. The perifusion of a normal concentration of Ca (2.3 mM) greatly stimulated (45)Ca efflux, indicating Ca <--> (45)Ca exchange. When Ca and glucose were superimposed, the effects on (45)Ca efflux and insulin release depended upon the order of presentation of the stimuli: when Ca was added to an ongoing 16.7-mM glucose perifusion, biphasic patterns of (45)Ca and insulin release were seen; when glucose was superimposed on a Ca perifusion, an inhibition of the Ca-stimulated (45)Ca efflux occurred, and a reduced but clearly biphasic insulin response was seen. The subsequent insulin off response after with-drawal of the glucose was also reduced. Mathematical "peeling" of (45)Ca efflux curves from unstimulated islets suggests that there are at least two, and probably three, different intracellular Ca compartments (not including the extracellular sucrose space). At the beginning of perifusion, these three compartments (I, II, III) contain 25, 56, and 19% of the intracellular (45)Ca, and their rates of efflux are 6.7, 1.2, and 0.1%/min, respectively. Glucose appears to suppress efflux from the largest compartment (II); Ca appears to exchange with (45)Ca from a more inert compartment (III). The relationship between insulin and (45)Ca release is not stoichiometric.
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PMID:Glucose-stimulated 45Calcium efflux from isolated rat pancreatic islets. 35 48

Six normal weight subjects without any heredity of diabetes (group 1), 3 obese subjects with normal (group 2) and 9 with pathological carbohydrate tolerance (group 3) were characterized by a 2-h glucose infusion test. Adipose tissue fragments were obtained from the abdominal wall by surgical biopsy under intracutaneous anesthesia. Adipocytes were isolated by collagenase digestion and incubated in buffer containing [1-14C] glucose and different concentrations of insulin. The metabolic effect of insulin was expressed as percent increase above control 14CO2 production. Maximal CO2 raised to 207 +/- 25% and 154 +/- 9% in groups 1 and 2, respectively. These values were significantly higher than in obese subjects displaying a pathological carbohydrate tolerance (group 3; 119 +/- 6%). A negative correlation was found between blood glucose levels and biological activity of insulin on adipocytes. The results suggest that insulin sensitivity of target tissue seems to play an important role in development of carbohydrate intolerance.
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PMID:Relationship between carbohydrate tolerance, insulin secretion, and insulin sensitivity of isolated fat cells from obese protodiabetics. 36 Jul 50

Islets were isolated by mild collagenase digestion and microdissection from rat fetuses 2 days before term and pups 1 or 2 days after birth and their insulin and glucagon secretion studied in vitro. Fetal B cells were stimulated by 16.7 mmol/l glucose, 20 mmol/l leucine or 20 mmol/l arginine. Fetal A cells were not affected by glucose or leucine, but were significantly stimulated by arginine. Somatostatin abolished the effect or arginine on both IRI and IRG output. Neonatal islets proportionally released more insulin and glucagon than their fetal counterparts, but reacted to the tested agents in a similar fashion. During the perinatal period, pancreatic insulin storage increased at a higher rate than that of glucagon. It is concluded that fetal B cells are equipped with sensors to a variety of agents and able to modulate their secretory rate according to the concentration of these agents. A cells are reactive to arginine 2 days before term but do not become glucose reactive until several days after birth.
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PMID:Insulin and glucagon secretion by islets isolated from fetal and neonatal rats. 36 57


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