The stimulus-secretion coupling of glucose-induced insulin release. Does glycolysis control calcium transport in the B-cell?
1. The metabolism of glucose and the exchangeable Ca2+ pool were measured in rat pancreatic islets, in order to assess the possible significance of glycolysis in the process of glucose-induced insulin release. 2. At high glucose concentration (16.7 mM), glucose was metabolized at the following rate (pmol of glucose residue/h per islet +/- S.E.M.): 131 +/- 11 for glucose uptake, 129+/-8 for glucose utilization, as judged by the conversion of [5-3H]glucose into 3H2O,60+/-2 for lactate output and 25+/-2 for glucose oxidation. 3. The secretory pattern usually correlated with the metabolic data. For instance, the ability of different sugars (glucose, mannose, fructose, galactose, D-glyceraldehyde) to stimulate lactate output closely paralleled their relative insulinotropic capacity. A disparity between metabolic and secretory responses was, however, encountered in the presence of dibutyryl cyclic AMP and theophylline. 4. Despite this contrasting behaviour, the size of the Ca2+- exchangeable pool (net uptake of 45Ca2+) was invariably proportional to the rate of lactate output under all experimental conditions examined. It is concluded that glycolysis usually exerts a tight control on the rate constant for Ca2+ transport across the B-cell membrane.
D000818:Animals; D001692:Biological Transport; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D005690:Galactose / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D008356:Mannoheptulose / Q000494:pharmacology; D051381:Rats; D013806:Theophylline / Q000494:pharmacology
D007328:Insulin; D007773:Lactates; D003994:Bucladesine; D008356:Mannoheptulose; D013806:Theophylline; D005947:Glucose; D002118:Calcium; D005690:Galactose