MESENTERIC VASCULAR-RESPONSES TO VASOPRESSIN DURING DEVELOPMENT OF DOCA-SALT HYPERTENSION IN MALE AND FEMALE RATS

Deoxycorticosterone acetate (DOCA)-salt hypertension develops to a greater extent in male (M) than in female (F) rats. To determine the role of the vasculature, reactivity to arginine vasopressin (AVP) and prostanoid output were examined in the isolated perfused mesenteric vasculature of hypertensive (HT) and normotensive-control (NTC) M and F rats after acute (1-wk) and chronic (4-wk) DOCA-salt treatment. Systolic blood pressure was significantly higher in M than in F HT rats (187 +/- 3 vs. 151 +/- 3 mmHg after 4 wk; P < 0.02). After acute treatment, vascular reactivity to AVP (maximal perfusion pressure) in HT was elevated in M (181 +/- 18 mmHg; P < 0.02) but not in F (135 +/- 6 mmHg) compared with NTC (90 +/- 6 mmHg, M vs. 119 +/- 5 mmHg, F). After chronic treatment, vascular reactivity to AVP in HT was elevated in both sexes (P < 0.02), although more in F (175 +/- 13 mmHg) than in M (141 +/- 11 mmHg). In contrast, vascular responsiveness to phenylephrine did not differ significantly between M and F NTC or HT preparations after either acute or chronic treatment. Sex differences in basal and AVP-induced 6-ketoprostaglandin (6-keto-PG) F-1 alpha and PGE(2) output by HT and NTC vasculature were reciprocal to sex differences in the vasoconstriction responses to AVP. After acute treatment, AVP-stimulated 6-keto-PGF(1 alpha) output by HT was elevated slightly in F (33.6 +/- 1.7 ng/3 min; P less than or equal to 0.02) but not in M (49.9 +/- 4.3 ng/3 min) compared with NTC (23.5 +/- 2.6 ng/3 min, F vs. 34.7 +/- 4.9 ng/3 min, M). After chronic treatment, output by HT was enhanced in both sexes (P less than or equal to 0.02), although more in M (109 +/- 15.4 ng/3 min) than in F (68 +/- 6.6 ng/3 min). These findings suggest that sex differences in the relative balance between AVP-induced vasoconstriction and vasodilatory prostanoid release may contribute to male-female differences in mesenteric vascular reactivity to AVP in NT and that disturbances in this balance may be responsible, at least in part, for the sex- and time-dependent changes in reactivity to AVP observed during the development of DOCA-salt hypertension.