EFFECT OF HYPOPHYSECTOMY ON PLASMA-CATECHOLAMINES AND ENKEPHALINS IN FETAL SHEEP

The aim of this study was to determine the effect of fetal hypophysect omy on the plasma concentrations of catecholamines and enkephalins in the fetal sheep between 120 and 140 days gestation under basal and hyp oxic conditions. During basal conditions, there was no difference in t he plasma concentrations of norepinephrine and epinephrine between int act and hypophysectomized groups. Fetal plasma norepinephrine concentr ations were significantly increased during hypoxia in intact fetal she ep (7.2 +/- 2.2 pmol/ml, -15 min; 20.2 +/- 7.7 pmol/ml, 30 min) betwee n 130 and 140 days, but after fetal hypophysectomy there was no signif icant norepinephrine response to hypoxia at this gestational age (4.7 +/- 1.3 pmol/ml, -15 m in; 8.8 +/- 2.8 pmol/ml, 30 min). In contrast, fetal plasma epinephrine concentrations were significantly increased d uring hypoxia in both the intact (1.5 +/- 0.5 pmol/ml, -15 min; 3.3 +/ - 1.7 pmol/ml, 30 min) and hypophysectomized groups (1.8 +/- 0.6 pmol/ ml, -15 min; 6.8 +/- 4.1 pmol/ml, 30 min) between 130 and 140 days. Du ring basal conditions, plasma concentrations of free Met-Enk were sign ificantly less in hypophysectomized fetal sheep (170.8 +/- 34.3 pg/ml; 120-140 days) than in intact fetal sheep (305.6 +/- 47.3 pg/ml). Ther e were no differences, however, in the fetal plasma concentrations of total Met-Enk between the intact (18.0 +/- 1.9 ng/ml) and hypophysecto mized (16.9 +/- 2.6 ng/ml) groups. During hypoxia, there were no chang es in the fetal plasma concentrations of either free or total Met-Enk in the intact or hypophysectomized groups. We conclude, therefore, tha t fetal hypophysectomy differentially alters the capacity of the fetal sympathetic nervous system to synthesize and/or secrete norepinephrin e and free Met-Enk during basal and hypoxic conditions.