208 DEHYDROISOANDROSTERONE (D) AND OVINE FETAL ESTROGEN PRODUCTION

Abstract

Factors controlling uteroplacental blood flow are vaguely understood,but estrogen appears of importance. Systemic infusions of D into pregnant ewes result in increases in maternal estrone(E1), estradiol(E2),and uterine blood flow. Although D is a substrate for ovine estrogen production during pregnancy,the conversion site and fetal role are unknown. To investigate this 10 pregnant ewes, 124-150 days of gestation,were prepared with catheters in fetal umbilical vein(γ),femoral artery(α),and vena cava(fv),and maternal uterine vein(v),femoral artery(A),and vena cava(V),permitting simultaneous arteriovenous(a−v) sampling from fetal and maternal placental circulations. Uterine artery flow probes were placed in 4 ewes. After the 4th postop day simultaneous samples taken from A, v, α and γ prior to and 7.5,15,30,60,90,120,150 and 180 min. after the infusion of 6mg D into fv. Uterine blood flow rose 22 ± 9%*(Mean ± SE) at 110 min. At 7.5 min. ΔEl(pg/ml)was:A=281*,v= 653*,α=621*,γ=715*;ΔE2(pg/ml):A=51.6*,v=89.8*,α=307*,γ=295*;and Δ dehydroisoandrosterone sulfate(DS,ng/ml):A=66.9*,v=125*,α=1040*,γ=730*. In 3 fetuses D was measured in α and γ at 0 and 15 min,; Δ ng/ml=73.6 and 4.94,respectively. All values returned toward control levels after 180 min. The results of these studies are consistent with conversion of exogenous D by the fetal-placental unit to DS,E1 and E2. Although estrogen levels seen at the onset of parturition were achieved,parturition was not induced by D. Moreover,fetal-placental aromatase activity does not appear to be rate limiting in ovine estrogen production. *p < 0.05