Biomaterial Database

Secretion of insulin in a perifusion system and conversion of proinsulin to insulin by pancreatic islets from hyperglycemic rats. 1977

K Jain, and J Logothetopoulos

The secretory pattern of insulin and the rate of conversion of proinsulin to insulin were studied in isolated pancreatic islets from normoglycemic (buffer-infused for 24 hours) and hyperglycemic (glucose-infused for 24 hours) rats. The profiles of insulin secretion obtained during one hour of perifusion were markedly different in the two groups. The rate of insulin secretion by islets from the hyperglycemic rats was initially very high but progressively declined during the late period of the perifusion. The reverse pattern was found with the islets from buffer-infused rats. For the estimation of the rate of proinsulin conversion, islets were pulse-labeled with L-[4,5-3H]-leucine for 15 minutes and "chase"-incubated for 30 and 60 minutes. Labeled rat proinsulin and rat insulins in the medium and in the islet extracts were separated by a validated SDS-urea electrophoretic acrylamide procedure following immunoprecipitation. The conversion rate was estimated from the radioactivity in the insulin band, expressed as a per cent of the radioactivity in the proinsulin + insulin bands. Islets from hyperglycemic rats converted newly synthesized proinsulin to insulin at significantly higher rates than did control islets.

UI	MeSH Term	Description	Entries
D007328	Insulin	A 51-amino acid pancreatic hormone that plays a major role in the regulation of glucose metabolism, directly by suppressing endogenous glucose production (GLYCOGENOLYSIS; GLUCONEOGENESIS) and indirectly by suppressing GLUCAGON secretion and LIPOLYSIS. Native insulin is a globular protein comprised of a zinc-coordinated hexamer. Each insulin monomer containing two chains, A (21 residues) and B (30 residues), linked by two disulfide bonds. Insulin is used as a drug to control insulin-dependent diabetes mellitus (DIABETES MELLITUS, TYPE 1).	Iletin,Insulin A Chain,Insulin B Chain,Insulin, Regular,Novolin,Sodium Insulin,Soluble Insulin,Chain, Insulin B,Insulin, Sodium,Insulin, Soluble,Regular Insulin
D007515	Islets of Langerhans	Irregular microscopic structures consisting of cords of endocrine cells that are scattered throughout the PANCREAS among the exocrine acini. Each islet is surrounded by connective tissue fibers and penetrated by a network of capillaries. There are four major cell types. The most abundant beta cells (50-80%) secrete INSULIN. Alpha cells (5-20%) secrete GLUCAGON. PP cells (10-35%) secrete PANCREATIC POLYPEPTIDE. Delta cells (~5%) secrete SOMATOSTATIN.	Islands of Langerhans,Islet Cells,Nesidioblasts,Pancreas, Endocrine,Pancreatic Islets,Cell, Islet,Cells, Islet,Endocrine Pancreas,Islet Cell,Islet, Pancreatic,Islets, Pancreatic,Langerhans Islands,Langerhans Islets,Nesidioblast,Pancreatic Islet
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D007930	Leucine	An essential branched-chain amino acid important for hemoglobin formation.	L-Leucine,Leucine, L-Isomer,L-Isomer Leucine,Leucine, L Isomer
D008297	Male		Males
D011384	Proinsulin	A pancreatic polypeptide of about 110 amino acids, depending on the species, that is the precursor of insulin. Proinsulin, produced by the PANCREATIC BETA CELLS, is comprised sequentially of the N-terminal B-chain, the proteolytically removable connecting C-peptide, and the C-terminal A-chain. It also contains three disulfide bonds, two between A-chain and B-chain. After cleavage at two locations, insulin and C-peptide are the secreted products. Intact proinsulin with low bioactivity also is secreted in small amounts.
D005947	Glucose	A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement.	Dextrose,Anhydrous Dextrose,D-Glucose,Glucose Monohydrate,Glucose, (DL)-Isomer,Glucose, (alpha-D)-Isomer,Glucose, (beta-D)-Isomer,D Glucose,Dextrose, Anhydrous,Monohydrate, Glucose
D006943	Hyperglycemia	Abnormally high BLOOD GLUCOSE level.	Postprandial Hyperglycemia,Hyperglycemia, Postprandial,Hyperglycemias,Hyperglycemias, Postprandial,Postprandial Hyperglycemias
D000078790	Insulin Secretion	Production and release of insulin from PANCREATIC BETA CELLS that primarily occurs in response to elevated BLOOD GLUCOSE levels.	Secretion, Insulin
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia