Effects of insulin on thyrotropin releasing hormone from frog skin

Thyrotropin releasing hormone (TRH) is concentrated in the skin of Rana nigromacula. Its elution profile on Sephadex G-10 was identical to that of synthetic TRH. Insulin and noradrenaline stimulated TRH release from frog skin in a dose-related manner. The effects of insulin were not blocked by preincubation with phentolamine and they enhanced the noradrenaline effect. These data indicate that insulin stimulates directly TRH release from frog skin in other than the sympathetic pathway.