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Glucocorticoids Decrease Phenylethanolamine N ‐Methyltransferase mRNA Expression in the Immature Foetal Sheep Adrenal
Author(s) -
Michael Brenton Adams,
J. T. Ross,
Timothy G. Butler,
I. Caroline McMillen
Publication year - 1999
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1046/j.1365-2826.1999.00359.x
Subject(s) - endocrinology , medicine , phenylethanolamine , proenkephalin , adrenal medulla , phenylethanolamine n methyltransferase , adrenal gland , catecholamine , saline , glucocorticoid , biology , tyrosine hydroxylase , messenger rna , dopamine , enkephalin , biochemistry , receptor , opioid , gene
This 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.