Adams, M.B.Ross, J.T.Butler, T.G.McMillen, I.C.2020-03-172020-03-171999Journal of Neuroendocrinology, 1999; 11(7):569-5750953-81941365-2826http://hdl.handle.net/2440/123688This study examined the impact of a chronic physiological elevation of plasma cortisol levels on adrenal catecholamine synthetic enzyme and proenkephalin A mRNA expression in foetal sheep. Cortisol (2.5-3. 0 mg.5 ml-1.24 h-1, n=9) or saline (0.9% saline, n=6) was infused into foetal sheep for 7 days between 109 days and 116 days gestation. Foetal plasma cortisol concentrations were higher (P<0.0005) in the cortisol infused foetuses when compared with the saline infused group (43.07+/-4.13 nmol.l-1 vs 1.67+/-0.10 nmol.l-1). There were no differences, however, in the plasma ACTH levels between the two groups. Using Northern blot analysis, adrenal phenylethanolamine N-methyltransferase (PNMT) mRNA expression was found to be reduced (P<0.005) fivefold in the cortisol infused foetuses when compared with the controls, as was the relative area of the adrenal medulla which stained positively with anti-PNMT (28.1+/-2.5% vs 44.8+/-4.8%, P<0.007). No effect of cortisol infusion was observed on adrenal tyrosine hydroxylase mRNA and protein expression or proenkephalin A mRNA expression. We conclude that before birth, adrenaline synthesis may be suppressed by a novel direct, or indirect, inhibitory effect of glucocorticoids on PNMT mRNA expression.en© 1999 Blackwell Science Ltdtyrosine hydroxylase; catecholamines; proenkephalin A; adrenal medulla; cortisolJournal article003008061310.1046/j.1365-2826.1999.00359.x0000815983000102-s2.0-0032998085392547Ross, J.T. [0000-0001-7243-1051]