Biomaterial Database

Insulin release and the microtubular system of the islets of Langerhans: effects of insulin secretagogues on microtubule subunit pool size. 1976

W Montague, and S L Howell, and I C Green

An assay system was devised to estimate the pool size of microtubule subunits in islet cells, and to study the importance of the equilibrium between polymerised microtubules and their subunits in the regulation of insulin release. The assay was based on the observation that colchicine binds specifically and quantitatively to microtubule protein subunits, but not to intact microtubules. Vinblastine and cold treatment, which have been shown to cause disaggregation of microtubules into subunits and to inhibit insulin release from islets, increased the number of colchicine binding subunits. D2O, which promotoes stability of microtubules and increases their number in islet cells, caused a decrease in subunit concentration. These results suggest that changes in the equilibrium between polymerised microtubules and their subunits could be studied by measuring the size of the subunit pool. When insulin release was stimulated, by incubating islets in high glucose concentrations or by increasing the intracellular concentration of cyclic AMP there was a reduction in the content of subunit protein. Conversely, when insulin release was inhibited by removal of calcium from the incubation medium there was a shift in the microtubule subunit equilibrium to give an increase in the number of subunits assayed. These results indicate that changes in the equilibrium between subunits and microtubules may play an important role in regulating rates of insulin secretion.

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
D008870	Microtubules	Slender, cylindrical filaments found in the cytoskeleton of plant and animal cells. They are composed of the protein TUBULIN and are influenced by TUBULIN MODULATORS.	Microtubule
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003078	Colchicine	A major alkaloid from Colchicum autumnale L. and found also in other Colchicum species. Its primary therapeutic use is in the treatment of gout, but it has been used also in the therapy of familial Mediterranean fever (PERIODIC DISEASE).	Colchicine, (+-)-Isomer,Colchicine, (R)-Isomer
D003080	Cold Temperature	An absence of warmth or heat or a temperature notably below an accustomed norm.	Cold,Cold Temperatures,Temperature, Cold,Temperatures, Cold
D003903	Deuterium	The stable isotope of hydrogen. It has one neutron and one proton in the nucleus.	Deuterons,Hydrogen-2,Hydrogen 2
D005260	Female		Females
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