Forskolin-induced activation of adenylate cyclase, cyclic adenosine monophosphate production and insulin release in rat pancreatic islets |
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Authors: | W J Malaisse P Garcia-Morales S P Dufrane A Sener I Valverde |
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Abstract: | Forskolin activated adenylate cyclase in rat islet homogenates and stimulated cAMP production in intact islets incubated in the absence or presence of either D-glucose or Ca2+. Forskolin failed to affect D-[U-14C]glucose oxidation, glucose-stimulated net 45Ca uptake, or basal insulin release, but enhanced insulin secretion evoked by either nutrients (D-glucose, 2-ketoisocaproate, L-leucine alone or in combination with L-glutamine), or nonnutrient secretagogues (12-O-tetradecanoylphorbol-13-acetate, Ba2+ alone or in combination with theophylline). Forskolin stimulated insulin release from islets incubated in the presence of glucose but in the absence of Ca2+. These findings confirm that a marked increase in cAMP production is not sufficient to cause sustained insulin release. They also suggest that the enhancing action of endogenous cAMP upon insulin release does not depend on a facilitation of Ca2+ influx into islet cells. |
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