A possible explanation of genetic hypertension in the spontaneously hypertensive rat.
Converting enzyme inhibitors prevent the development of hypertension and normalize arterial blood pressure in spontaneously hypertensive rats (SHR), suggesting a critical role for angiotensin II in genetic hypertension. We hypothesized that the SHR is hyperresponsive to the slow-pressor effect of angiotensin II. To test this hypothesis, 14 SHR and 14 normotensive Wistar Kyoto rats (WKY) were treated chronically with captopril (100 mg X kg-1 X day-1 in drinking water) beginning at 5 weeks of age. At 9 weeks of age, either angiotensin II (125 ng/min; 7 SHR and 7 WKY) or vehicle (7 SHR and 7 WKY) was infused for 2 weeks via an osmotic minipump implanted into the peritoneal cavity. Captopril treatment was maintained and systolic blood pressure was monitored 3 times weekly. Although systolic blood pressure was similar in SHR and WKY infused with vehicle (101 +/- 2 versus 103 +/- 5 mmHg, respectively during the second week), systolic blood pressure in SHR treated with angiotensin II was much greater than systolic blood pressure in WKY treated with angiotensin II (193 +/- 9 versus 132 +/- 11 mmHg, respectively during the second week, p less than 0.001). These results indicate that compared to WKY, SHR are remarkably more sensitive to the slow-pressor effect of chronic, low-dose infusions of angiotensin II. Our results support the hypothesis that the critical genetic defect in SHR is a change in the sensitivity to the slow-pressor effect of angiotensin II.
Li
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Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232.
Jackson
E K
EK
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002216:Captopril / Q000494:pharmacology; D006973:Hypertension / Q000235:genetics* / Q000517:prevention & control; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000806:Angiotensin-Converting Enzyme Inhibitors; D002216:Captopril