Failure of ergotamine to alter the lipolytic effect of somatotropin in dogs.

Hypophysectomized dogs were injected intravenously with bovine somatotropin (GH), and plasma free fatty acid (FFA) concentrations were measured over a period of 2 h. The response consisted of an initial reduction in the concentration of plasma FFA followed by a rebound and a delayed rise above baseline values. When the animals were given a single intravenous injection of ergotamine tartrate 30 min prior to the administration of GH, the biphasic pattern with the sluggish rise in plasma FFA was retained. This finding is contrary to the results of identical experiments conducted by us with dihydroergotamine, which proved to be a potent amplifier of the lipolytic effect of GH. Since the only difference between these two compounds is the presence or absence of the double bond at C9 and C10 of the lysergic acid moiety, it appears that unless this bond is saturated the alkaloid is not capable of functioning as a biological amplifier.