Regulation of plasma insulin level by alpha 2-adrenergic receptors.

Phentolamine, yohimbine or dihydroergotamine markedly increased plasma immunoreactive insulin (IRI) and inhibited epinephrine-induced hyperglycemia in fasted mice. On the other hand, phenoxybenzamine or prazosin only slightly increased plasma IRI and enhanced epinephrine-induced hyperglycemia. These results indicate that there is a distinct difference in the effects of alpha-adrenergic blockers on the plasma IRI and glucose levels, and that alpha-adrenergic receptors responsible for the plasma IRI level resemble alpha 2-adrenergic receptors more closely.