17β-Hydroxysteroid Dehydrogenase Activity in Tissues of Fetal Rhesus Macaques

Abstract

Abstract

17β-Hydroxysteroid dehydrogenase (17β-HSDH) activity was measured in tissues (anterior pituitary, diencephalon, frontal cortex, liver, whole blood, and uterus) of fetal rhesus macaques on Days 80, 120, and 150 of gestation. The production of estrone (E₁ (quantified by radioimmunoassay) by an 800g supernatant incubated with excess substrate (estradiol-17β [E₂]) was used as an index of 17β-HSDH activity. Over a 30-min incubation period E₁ was produced in a linear fashion by all the tissues that we studied. The pH optimum for this activity in the pituitary gland was ~9. Boiling of the tissue for 1 min reduced its activity significantly. Significant changes in 17β-HSDH activity during development were observed for two of the six tissues studied. Activity in fetal anterior pituitary glands was greatest on Day 80 of gestation but changed to significantly lower levels by Day 120 (P < 0.01). This low level continued on Day 150 of gestation. The pattern of activity in the liver was different from that in the pituitary gland. High activity was found on Day 80, and this increased significantly by Day 120 (P < 0.05). The levels of activity observed on Day 150 were similar to those found on Day 120. Low levels of 17β-HSDH activity were found in the central nervous system, whole blood, and uterus. In rhesus adults as in fetuses we have found relatively high levels of 17β-HSDH activity in the anterior pituitary gland. The biological significance of changing levels of this activity during gestation is not known.