Abstract
We previously reported that male spontaneously hypertensive rats (SHRs) are more sensitive to chronic angiotensin (Ang) II-induced hypertension compared with female rats. This study was designed to test the hypothesis that anesthetized male SHRs are also more responsive to acute Ang II-induced increases in blood pressure and renal hemodynamic changes when compared with female SHRs. Baseline mean arterial pressure (MAP) was higher in male SHRs than in female SHRs (135 ± 2 vs. 124 ± 4 mmHg, P < 0.05). Acute intravenous infusion of Ang II (5 ng/kg/min) for 60 minutes significantly increased MAP to 148 ± 2 mmHg in male SHRs (P < 0.05) without a significant change in MAP in female SHRs. Baseline glomerular filtration rate (GFR) was also higher in male SHRs than in female SHRs (2.6 ± 0.3 vs. 1.3 ± 0.1 mL/min, P < 0.05). Ang II infusion for 60 min significantly decreased GFR in male SHRs (2.0 ± 0.2 mL/min; P < 0.05) without significant changes in urine flow rate, sodium, or chloride excretion. In contrast, Ang II infusion increased GFR in female SHRs (1.9 ± 0.2 mL/min; P < 0.05). The increase in GFR upon Ang II infusion in female SHRs was associated with increases in urine flow rate (4.3 ± 0.3 to 7.1 ± 0.9 μL/min), sodium excretion (0.16 ± 0.04 to 0.4 ± 0.1 μmol/min), and chloride excretion (0.7 ± 0.08 to 1.1 ± 0.1 μmol/min; for all P < 0.05). These findings support the hypothesis that there is sex difference in response to acute Ang II infusion in SHRs with females being less responsive to Ang II-induced elevations in blood pressure and decreases in GFR relative to male SHRs.