Abstract

Administration of N-isopropyl methoxamine (IMA) lowered markedly the fasting plasma free fatty acids (FFA) of the conscious dog and man. Comparative experiments with the D- and L- isomers of the drug showed that this activity resides in the L- form. IMA blocked the marked elevation of plasma FFA and triglycerides which occurs in the dog exposed to a cold environment. The cold-induced rise of circulating FFA was blocked with difficulty in the rat presumably because this species metabolizes the drug at a much more rapid rate than the dog. Man and dog metabolize IMA at about the same rate with a biological half-life of about 6 hours. Since IMA has been shown to exert a potent effect in blocking the catecholamine-induced release of FFA, the results presented here provide additional evidence for the requirement of the sympathetic nervous system in the mobilization of FFA.