Estrogen and salt sensitivity in the female mRen(2). Lewis rat

The present study determined whether early loss of estrogen influences salt-sensitive changes in blood pressure, renal injury, and cardiac hypertrophy as well as the effects on the circulating renin-angiotensin-aldosterone system (RAAS) in the hypertensive female mRen(2). Lewis strain. Ovariectomy (OVX) of heterozygous mRen(2). Lewis rats on a normal salt (NS) diet (0.5% sodium) increased systolic blood pressure from 137 +/- 3 to 177 +/- 5 mmHg (P < 0.01) by 15 wk but did not show any changes in cardiac-to-body weight index (CI), proteinuria, or creatinine clearance. Maintenance with a high-sodium (HS) diet (4%) increased blood pressure (203 +/- 4 mmHg, P < 0.01), proteinuria (3.5 +/- 0.3 vs. 6.4 +/- 0.7 mg/day, P < 0.05), and CI (4.0 +/- 0.1 vs. 5.2 +/- 0.1 mg/kg, P < 0.01) but decreased creatinine clearance (0.89 +/- 0.15 vs. 0.54 +/- 0.06 ml/min, P < 0.05). OVX exacerbated the effects of salt on the degree of hypertension (230 +/- 5 mmHg), CI (5.6 +/- 0.2 mg/kg), and proteinuria (13 +/- 3.0 mg/day). OVX increased the urinary excretion of aldosterone approximately twofold in animals on the NS diet (3.8 +/- 0.5 vs. 6.6 +/- 0.5 ng center dot mg creatinine(-1)(.)day(-1), P < 0.05) and HS diet (1.4 +/- 0.2 vs. 4.5 +/- 1.0 ng center dot mg creatinine(-1)(.)day(-1), P < 0.05). Circulating renin, angiotensin-converting enzyme, and angiotensin II were also significantly increased in the OVX group fed a HS diet. These results reveal that the protective effects of estrogen apart from the increase in blood pressure were only manifested in the setting of a chronic HS diet and suggest that the underlying sodium status may have an important influence on the overall effect of reduced estrogen.