Enhancement of insulin secretion during selective blockade of alpha 1- and alpha 2-adrenoceptors in the rat: effects of somatostatin.
The effects of somatostatin on plasma concentrations of insulin and glucose in the presence of the selective alpha 1-adrenoceptor blocking agent prazosin or the selective alpha 2-adrenoceptor blocking drug yohimbine were studied in vivo in anesthetized rats. Infusion of both prazosin (0.080 mg/min) and yohimbine (0.018 mg/min) increased plasma insulin levels within 10 min. Prazosin, but not yohimbine, caused a significant increment in plasma glucose concentrations during the infusion of both prazosin and yohimbine, suggesting that the inhibitory effect of somatostatin is not mediated via a direct action on alpha 1- or alpha 2-adrenoceptors. Plasma glucose concentration fell slightly during somatostatin administration. A marked increment in insulin release occurred in response to cessation of the somatostatin infusion, both during prazosin- and yohimbine-treatment. We conclude that somatostatin efficiently inhibits insulin secretion during selective alpha 1- and alpha 2-adrenoceptor blockade and, further, that the insulin off-response after somatostatin treatment is potentiated by alpha-adrenoceptor blockade. This study also indicates that blockade of alpha 1- as well as alpha 2-adrenoceptors leads to an increased insulin secretion.
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D007328:Insulin / Q000097:blood*; D008297:Male; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D013004:Somatostatin / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D000317:Adrenergic alpha-Antagonists; D001786:Blood Glucose; D007328:Insulin; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D013004:Somatostatin; D011224:Prazosin