Estradiol-17β (E2) produces vasodilation in several systemic vascular beds, but most extensively in the nonpregnant uterus. It has been postulated that E2 induces this vasodilation via blockade of vascular α-adrenergic receptors. This hypothesis was tested in six chronically instrumented, nonpregnant sheep by comparing the systemic and uterine hemodynamic responses to intravenous E2, to an α-adrenergic receptor blocker, phentolamine, and to both agents given together. Uterine blood flow (UBF) increased significantly after E2 administration, from 20 ± 7 to 233 ± 37 (SE) ml/min. In contrast, phentolamine had no detectable effect on UBF or on the UBF response to E2 when both were given together. Similar contrasting responses were observed in the effects of E2 and/or phentolamine on the systemic vasculature. When responses to α-agonists were evaluated, there was no evidence of α-blockade following E2 despite the substantial vasodilation; in contrast, α-blockade was present during phentolamine administration when no vasodilation was noted. Therefore, we conclude that E2-induced vasodilation in chronically instrumented sheep is not mediated through blockade of vascular α-adrenergic receptors.
|American Journal of Physiology - Heart and Circulatory Physiology
|Published - 1985
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)