Reserpine-induced supersensitivity in adenylate cyclase preparations from guinea-pig heart

The effects of a reserpine treatment inducing supersensitivity to the cardiac effects of agonists (2.5 mg/kg per day for 2 days) was studied on guinea-pig cardiac adenylate cyclase (AC) activity. Reserpine treatment had no effect on basal or Gpp(NH)p (10(-7) M)-stimulated activities. Histamine (2 X 10(-6) and 10(-4) M) stimulation of guinea-pig AC was not influenced by the reserpine treatment. Epinephrine stimulation of AC was affected by reserpine and was characterized by an upward shift of the epinephrine dose-response curve with no change in the epinephrine EC50. The results indicate that the enhancement of cyclic AMP production is an important factor in the reserpine-induced cardiac supersensitivity to beta-adrenoceptor agonists.