Epinephrine-induced cyclic AMP production and vasoconstriction in the noncyclically perfused rat hindlimb: A possible role for insulin

Abstract

The effects of epinephrine alone and in combination with insulin and adrenergic blocking agents on cyclic AMP production and vascular tone are studied in noncyclically perfused rat hindlimbs. Epinephrine increases cyclic AMP production 11-fold and vascular resistance 2-fold. Insulin has no effect on either parameter but blunts cyclic AMP production in response to epinephrine by 50% without altering the epinephrine induced change in resistance. Alpha and beta adrenergic blocking agents have divergent and contrasting effects when infused with epinephrine. Phentolamine, but not propranolol, blocks the increase in vascular resistance observed with epinephrine; propranolol, but not phentolamine, inhibits epinephrine stimulated cyclic AMP release. These studies suggest that cyclic AMP may not play a significant role in alpha adrenergic mediated vasoconstriction.