Sex differences in the pressor response to angiotensin II when the endogenous renin-angiotensin system is blocked

The present study determined whether there are sex differences in the pressor response to angiotensin II (Ang II) when the endogenous renin-angiotensin system (RAS) is blocked by enalapril (ACEI), and whether this pressor response is changed in the presence of high salt (HS). Telemetry BP was measured in rats treated with ACEI (250 mg/L drinking water) (n = 6 to 7/grp), or with ACEI and Ang II (150 ng/kg/min, sc; n = 5 to 6/grp), for 3 wk. For the last 2 wk of the study, rats received HS (4% NaCl). MAP was lower in females during baseline (100.8 +/- 1.1 versus 105.2 +/- 1.3; P < 0.05), and with ACEI the last 3 days on normal salt diet ( 78.8 +/- 1.2 versus 88.5 +/- 0.9; P < 0.05), but increased to higher levels than in males on day 6 of Ang II ( 129.0 +/- 2.2 versus 117.3 +/- 2.9; P < 0.05). One week of Ang II increased albuminuria in males, but not females, and urinary 8-iso-PGF2 alpha(F2-isoP) was not increased in either males or females. MAP was salt-sensitive in both sexes receiving ACEI, but was only salt-sensitive in males with Ang II (129.3 +/- 3.7 versus 145.1 +/- 5.7; P < 0.05). Albuminuria continued to increase with HS and Ang II in males, but not in females. F2-isoP excretion increased with MAP during the last week of HS and Ang II in males but was independent of MAP in females. With ACEI, MAP in females on normal salt is more responsive to Ang II but is independent of oxidative stress or renal injury. MAP in males is salt-sensitive with Ang II, which may be mediated by oxidative stress and renal injury.