Biomaterial Database

Studies on the function of pancreatic islet cell membranes. 1976

L A Idahl, and A Lernmark, and J Sehlin, and I B Täljedal

Pancreatic islets rich in beta-cells were isolated from non-inbred ob/ob-mice and used for studying various aspects of the function of the plasma membrane. A review is given of the authors' work along the following lines: the role of transmembrane transport or membrane binding in the recognition of insulin-releasing sugars, amino acids, sulfonylureas, and sulphydryl-blocking agents; the role of cyclic 3',5'-AMP and cations in the coupling of stimulus recognition to insulin discharge; alloxan beta-cytotoxicity in vitro and its prevention by sugars; the isolation of a subcellular fraction enriched by plasma membranes. 1. It is suggested that D-glucose is recognized as an insulin secretagogue by being metabolized in the beta-cells; the teleological purpose of the transmembrane transport system being to allow fluctuations of the extracellular glucose concentration to be rapidly transmitted to the cell interior. Insulin-releasing sulfonyluraes and sulphydryl reagents are thought to act directly on the beta-cell plasma membrane, however. 2. Although cyclic 3',5'-AMP may amplify the expression of a secretory signal induced by D-glucose, studies with cholera toxin suggest that activation of the adenylate cyclase does not per se elicit secretion. The increase of islet cyclic 3',5'-AMP observed in response to several secretagogues, including D-glucose, may be secondary to membrane depolarization. 3. The possible role of an electrodiffusional mechanism in controlling the electrical potential is emphasized; a decrease of K+ permeability, rather than an increase of Na+ permeability, is suggested to be involved in the depolarizing action of D-glucose. Studies with the lanthanum-wash technique indicated that D-glucose causes a net flux of Ca2+ from the outside to the inside of the beta-cells. Although this uptake may relate to the enhancement of insulin secretion, the detailed mechanisms are unclear. 4. Inhibition of the Na+/K+ pump may be one of the earliest events in damage to the beta-cell by alloxan, on the basis of Rb+ studies. Protective effects of glucose against alloxan toxicity appear to be close related. 5. Studies of enzyme markers, the binding of wheat germ agglutinin, and electron microscopy indicate the presence of plasma membranes in a smooth-membrane fraction obtained by fractionating islet homogenates at consecutive sucrose gradients.

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
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
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
D000078790	Insulin Secretion	Production and release of insulin from PANCREATIC BETA CELLS that primarily occurs in response to elevated BLOOD GLUCOSE levels.	Secretion, Insulin
D000242	Cyclic AMP	An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.	Adenosine Cyclic 3',5'-Monophosphate,Adenosine Cyclic 3,5 Monophosphate,Adenosine Cyclic Monophosphate,Adenosine Cyclic-3',5'-Monophosphate,Cyclic AMP, (R)-Isomer,Cyclic AMP, Disodium Salt,Cyclic AMP, Monoammonium Salt,Cyclic AMP, Monopotassium Salt,Cyclic AMP, Monosodium Salt,Cyclic AMP, Sodium Salt,3',5'-Monophosphate, Adenosine Cyclic,AMP, Cyclic,Adenosine Cyclic 3',5' Monophosphate,Cyclic 3',5'-Monophosphate, Adenosine,Cyclic Monophosphate, Adenosine,Cyclic-3',5'-Monophosphate, Adenosine,Monophosphate, Adenosine Cyclic
D000496	Alloxan	Acidic compound formed by oxidation of URIC ACID. It is isolated as an efflorescent crystalline hydrate.
D000606	Amino Sugars	SUGARS containing an amino group. GLYCOSYLATION of other compounds with these amino sugars results in AMINOGLYCOSIDES.	Amino Sugar,Sugar, Amino,Sugars, Amino
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
D001692	Biological Transport	The movement of materials (including biochemical substances and drugs) through a biological system at the cellular level. The transport can be across cell membranes and epithelial layers. It also can occur within intracellular compartments and extracellular compartments.	Transport, Biological,Biologic Transport,Transport, Biologic