Glucose dose-related influence of phospholipase C and melittin on insulin release from perifused rat islets.
We studied the influence of exogenous phospholipase C (20 mU/ml) and melittin (25 micrograms/ml) on glucose-induced insulin release to further assess the role of Pl turnover as an important component in signal transduction in the B-cells. The secretory response to both substances was rapid and biphasic. However, phospholipase C did not, like melittin, elicit a secretory response in the absence of glucose. Phospholipase C elicited a half-maximal response at 4.5 mM and melittin at 2.0 mM glucose. Phospholipase C also enhanced the maximum amount of insulin release. Mannoheptulose markedly inhibited the secretory response of both melittin and phospholipase C in the presence of glucose, but the secretory effect of melittin, in the absence of glucose was not influenced. The results indicate that both melittin and phospholipase C elicit a secretory effect dependent on intact glucose metabolism. However, the variability of the effects of each agent on the glucose-dose related secretory response indicates that melittin may influence insulin release in a manner independent of nutrient metabolism and phospholipase C activity.
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Department of Physiology & Biophysics, University of Alabama, Birmingham 35294.
D000818:Animals; D001514:Bee Venoms / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008356:Mannoheptulose / Q000494:pharmacology; D008555:Melitten / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012636:Secretory Rate / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000494:pharmacology*
D001514:Bee Venoms; D007328:Insulin; D008555:Melitten; D008356:Mannoheptulose; D010738:Type C Phospholipases; D005947:Glucose