Plasma dehydroepiandrosterone sulfate (DHAS)concentrations increase markedly inthe rhesus monkey fetus at the end of gestation. A further increase occurs in the infantTodetermine whether the changes in plasma concentration betweenthe fetus and infant represent maintenance of DHAS production by the infant adrenal gland, we measured the t1/2, distribution volume (VD), MCR, and production rate of DHAS in the late gestation rhesus monkey fetus (129-155 days gestation; term is 165 days) and infant (14-42days of age). A single bolus dose of [3H]DHAS was injected into five fetuses and four infants, andblood samples were collected serially from 5 min to 24 h after the injection. The amount of [3H]DHAS in the circulation was measured aftersolvolysis, extraction, and Celite chromatography. The concentration of DHAS in each sample was measured by RIA. DHAS wascleared significantly more rapidly in the fetus than in the infant [MCR in fetus, 2.4 ± 0.4 (±SE); MCR in infant, 0.6 ± 0.2 liters day-1 kg-1]. The t1/2 of DHAS was shorter in the fetus than inthe infant(1.0 ± 0.1 us. 3.3 ± 0.7 h). Absolute VD values were larger in thefetus than inthe infant(231 ± 29 and 143.8 ± 11.6 ml kg-1); however, they were similar when the fetal VD was calculated including placental weight as a component of fetal weight. The production rate of DHAS, calculated as the product of MCR and integrated plasma DHAS concentrationfor the duration of the experiment, was not significantly differentbetween the fetus and the infant (1.0 ± 0.2 and 3.3 ± 1.2 mg kg-1 day-1) in spite of the marked differences in plasma DHAS concentrations (445.8 ± 103.8 ng ml-1 in the fetus and 5165 ± 1296 ng ml-1 inthe infant). These results indicate that the adrenal of the infantrhesus monkey continuesto secrete DHASat a rate at least as high as that in the late gestation fetus. Since the infant maintains DHAS production similar to that of the fetus in the absence of the placenta, a corollary of these studies is that the elevated DHAS secretion in the rhesus infant is independent of the placenta or the hormonal milieu of pregnancy. The maintenance of a functional fetal zone in the adrenal gland makes the rhesus infant a suitable model to use in studyingthe regulation of DHAS secretion and fetal zone morphology.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Clinical Biochemistry
- Biochemistry, medical