17-BETA-ESTRADIOL STIMULATES FLOW-INDUCED VASODILATATION IN ISOLATED SMALL MESENTERIC-ARTERIES FROM PREPUBERTAL FEMALE RATS

OBJECTIVE: Flow-induced vasodilatation may contribute to lowering of p eripheral resistance to pregnancy. This study investigated modulation of flow responses by 17 beta-estradiol. STUDY DESIGN: Small mesenteric arteries from prepubertal female Wistar rats were pretreated for 3 ho urs with 17 beta-estradiol (10(-7) mol/L) with 17 alpha-estradiol (10( -7) mol/L) or vehicle (0.1% dimethylsulfoxide). Responses to intralumi nal flow were evaluated with use of a pressure arteriograph. RESULTS: After pretreatment with 17 beta-estradiol arteries relaxed to flow, wh ereas those treated with vehicle or 17 alpha-estradiol did not (percen t change in diameter at maximum flow rate after 17 beta-estradiol 38.7 % +/- 5.7%, n = 10, vs 1.1% +/- 4.3%, n = 10 after vehicle; p < 0.01). Endothelium removal or pretreatment with either a nitric oxide syntha se inhibitor or a novel soluble guanylyl cyclase inhibitor diminished the response to 17 beta-estradiol. CONCLUSION: 17 beta-Estradiol stimu lated nitric oxide-mediated flow-induced relaxation. Through this path way 17 beta-estradiol could play an important role in the control of v ascular tone.