Effects of alpha-adrenoceptor agonists and antagonists on insulin secreting cells and pancreatic blood vessels: comparative study.
The effects of alpha-adrenergic drugs were studied on glucose-induced insulin secretion and effluent flow rate on the same preparation: the isolated perfused rat pancreas. An alpha 1-adrenoceptor agonist, phenylephrine 0.05 microM slightly decreased insulin secretion (-25%); this inhibition was counteracted by an alpha 2-adrenoceptor antagonist, yohimbine 0.6 microM. Phenylephrine evoked a fall in liquid flow rate (-13%) which was reversed by an alpha 1-adrenoceptor antagonist, prazosin 6 microM, but not by yohimbine. An alpha 2-adrenoceptor agonist, clonidine 0.01 and 0.05 microM decreased insulin secretion (-80%). This inhibition was reversed by yohimbine 0.6 and 6 microM respectively. Only the concentration of 0.05 microM clonidine evoked a fall (-25%) in liquid flow rate; this fall was counteracted by yohimbine 0.6 microM. In conclusion our results show that adrenergic inhibition of insulin secretion is mediated only by alpha 2-receptors whereas both types of adrenoceptors are implicated in the vasoconstrictor effect. The insulin inhibitory effect of adrenoceptor agonists is not related to vasoconstriction.
Hillaire-Buys
D
D
Gross
R
R
Blayac
J P
JP
Ribes
G
G
Loubatières-Mariani
M M
MM
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001783:Blood Flow Velocity / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D010179:Pancreas / Q000098:blood supply / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014661:Vasoconstriction / Q000187:drug effects; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D007328:Insulin; D010656:Phenylephrine; D015016:Yohimbine; D003000:Clonidine; D011224:Prazosin