Hormone ontogeny in the ovine fetus. VIII. The effect of thyrotropin-releasing factor on prolactin and growth hormone release in the fetus and neonate.

Abstract

As part of studies on the ontogeny of PRL secretion and regulation, the effect of TRF on PRL release was studied in the chronically catheterized ovine fetus and neonate. After a 2-h control period, 250 μg TRF were given by rapid iv injection to seven fetuses between 88—133 days gestation (term, 147 days) and five lambs between 4—17 days old. All animals exhibited a prompt increase in the concentration of plasma PRL. In three fetuses with basal PRL concentrations less than 10 ng/ml (88, 89, and 111 days old), PRL rose from a mean value of 3.1 ± 2.0 to 11.5 ± 5.6 (SE) ng/ml 15 min after TRF and was 10.7 ± 5.0 ng/ml at 90 min. In four fetuses with basal PRL concentrations greater than 10 ng/ml (112, 121, 124, and 133 days old), significantly (P ≪ 0.05) more PRL was secreted; the mean concentration of PRL increased from 36.9 ± 12.1 to 88.2 ± 21.7 ng/ml at 15 min and was 77.8 ± 22.8 ng/ml at 90 min. In five neonates (5, 6, 10, 10, and 17 days old), PRL rose from 13.1 ± 2.3 to 81.6 ± 20.1 ng/ml at 15 min and fe...