Membrane potential of vascular smooth muscle and hypertension in spontaneously hypertensive rats.

The resting membrane potential of tail arteries from spontaneously hypertensive rats (SHRs) and Wistar-Kyoto controls (WKYs) was compared. At 4-5 weeks old, the blood pressure and resting membrane potential of the SHRs was not significantly different from the WKYs. The blood pressure of 8- to 10-week-old SHRs increased significantly to 183 mmHg (1 mmHg = 133.322 Pa) from 127 mmHg at 4 weeks, and the membrane potential decreased from 60 to 51 mV. At 15 weeks of age, the blood pressure of the SHRs was 193 mmHg and the membrane potential was 49 mV. In WKYs, there was no significant change in membrane potential with age. The decrease in membrane potential in the SHRs is due to a decrease in the ouabain-sensitive electrogenic pumping. Chronic treatment of the SHRs with captopril (100 mg . kg-1 . day-1) prevented the increase in blood pressure and the decrease in membrane potential.