Studies on the distribution of phenylethanolamine N-methyltransferase and epinephrine in the rat

Using two independent criteria, we have found the enzyme phenylethanolamine N-methyltransferase (PNMT) to be present in the adrenals, lungs, brain stem, spleen, heart and skeletal muscle of the rat. The lungs contained more activity than the brain stem or any other extra-adrenal organ. PNMT was not detectable, however, in the kidneys, stomach, liver and plasma. Trace amounts of epinephrine were found in brain stem, lung and heart; norepinephrine, however, was the predominant catecholamine in these tissues. Substantial quantities of epinephrine were found in the adrenal and plasma of decapitated animals, but the latter were essentially eliminated by adrenal demedullation. Our data indicate that although the adrenal is the principal tissue source of epinephrine and PNMT in the rat, small amounts of both substances are present in several body organs.