Ontogeny of epinephrine metabolic pathways in the rat: role of glucocorticoids

Recent studies suggest that the initial expression of adrenal phenylethanol amine N-methyltransferase (PNMT) and epinephrine (E) are dependent upon sti mulation of adrenal glucocorticoid receptors. However, evidence suggests th at the expression of heart and brain PNMT is independent of glucocorticoids . We measured PNMT activity and E levels in adrenal, heart and head over th e latter half of gestation in rat fetuses treated chronically with glucocor ticoids, and in normal controls. Chronic glucocorticoid treatment ending on embryonic day (e)12 did not affect heart, head or trunk PNMT activity or E levels. In contrast, chronic glucocorticoid exposure ending e19 or e20 res ulted in marked increases in both PNMT and E in adrenal, heart and head tis sues. The elevation of E in all three tissues was unaffected by maternal ad renalectomy, indicating enhanced fetal E synthesis. In the absence of exoge nous glucocorticoid treatment heart PNMT activity peaked on e12, prior to t he earliest reported appearance of glucocorticoid receptors. We conclude th at expression of PNMT in all three tissues is glucocorticoid independent un til the latter part of gestation when it is readily enhanced by glucocortic oids. (C) 2000 ISDN. Published by Elsevier Science Ltd. All rights reserved .