THE EFFECT OF SYSTEMIC INFUSIONS OF DEHYDROISOANDROSTERONE (D) ON THE DISTRIBUTION OF UTERINE BLOOD FLOW (UBF) IN THE OVINE PREGNANCY

Abstract

Although estrogen is a potent vasodilator of the vascular beds of the ovine uterus, precursors of ovine estrogen remain unknown. Studies in our laboratories have shown increases in UBF and plasma estrone (E1) and eatradiol (E2) after systemic infusions of D in the pregnant ewe. To investigate the distribution of UBF after the infusion of 6 mg D, 4 pregnant ewes, 105 to 128 days of gestation, were studied with microspheres. Serial blood samples from 3 ewes showed increases at 15 min in E1 from 27.3±2.23 (mean ± SE) to 117 ± 13.2 pg/ml and in E2 from 34.3 ± 4.91 to 71.7 ± 5.21 pg/ml (p ≤ 0.05). At 140 min neither UBF nor placental blood flow was significantly altered. Endometrial blood flow increased from 176 ± 24 to 242 ± 32 ml/min (39%, P < 0.005) and myometrial blood flow rose from 35 ± 6.1 to 51 ± 8.4 ml/min (45%, p < 0.01). Mammary gland blood flow also rose. Of particular interest were the responses in cervical blood flow, rising from 3.18 ± 0.6 to 15.6 ± 2.0 ml/min (441%, p < 0.005), and vaginal blood flow from 0.175 ± 0.03 to 0.992 ± 0.15 ml/min·gm (476%, p < 0.01). These studies suggest that D may be an important estrogen precursor and the ovine estrogen surge observed at term may prepare the mammary, uterus, cervix and vagina for the process of parturition. Furthermore, the increase in UBF following an infusion of D reflects increased perfusion of non-placental tissues, supporting earlier observations that exogenous estrogen administration might have no beneficial effects for the fetus.