Infusion of prostaglandin (PG) E1 in anesthetized dogs significantly lowered circulating insulin levels and inhibited insulin responses following intravenous glucose. A similar trend was observed with PGE2. Alpha adrenergic blockade did not reverse the PGE1 effect. Epinephrine infusion also inhibited glucose-stimulated insulin secretion, an effect that was not reversed by indomethacin. Therefore, in this investigative model, PGE1 inhibited insulin secretion but no interdependency of PGE1 and alpha adrenergic effects were found.