Pressor responsiveness to vasopressin and angiotensin II in spontaneously hypertensive rats: Effects of dietary sodium.

Publisher Website
Google Scholar
Abstract
The effects of dietary Na on pressor responsiveness to arginine vasopressin (AVP) and angiotensin II (AH) were examined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). SHR (16) and WKY (19) were divided into 2 groups, which were maintained on high Na diets or low Na diets for 4 wk. At the end of the treatment with either diet, the rats were anesthetized with urethane and mean arterial pressure was recorded from the iliac artery. After pretreatment with i.v. phenoxybenzamine, the pressor responses to graded i.v. injections of AVP and A II were determined in each rat. The pressor responses to AVP or A II were significantly higher in SHR than in WKY. Na loading significantly increased the pressor responses to A II and significantly decreased plasma renin activity in both SHR and WKY. There was no difference in pressor responses to AVP between Na loading and restriction in both SHR and WKY. In WKY, plasma concentration of AVP was not affected by dietary Na, but in SHR, it was significanlty higher on high Na diet than on low Na diet. The secretion of AVP was shown to be increased in SHR with high Na intake. The i.v. injection of an AVP antiserum reduced arterial blood pressure substantially. AVP may function as a direct pressor agent in the maintenance of high blood pressure in SHR.