1983 Volume 139 Issue 1 Pages 51-59
ASHIDA, T., YAZAKI, Y., OHUCHI, Y., TANAKA, T. and IKEDA, M. Pressor Responsiveness to Vasopressin and Angiotensin II in Spontaneously Hypertensive Rats: Effects of Dietary Sodium. Tohoku J. exp. Med., 1983, 139 (1), 51-59 - The effects of dietary sodium on pressor responsiveness to arginine vasopressin (AVP) and angiotensin II (A II) were examined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Sixteen SHR and 19 WKY were divided into two groups, which were maintained on high sodium diets or low sodium diets for four weeks. 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 intravenous 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. Sodium loading significantly increased the pressor responses to A II and significantly decreased plasma renin activity in both SHR and WKY. On the other hand, there was no difference in pressor responses to AVP between sodium loading and restriction in both SHR and WKY. In WKY, plasma concentration of AVP was not affected by dietary sodium, but in SHR, it was significantly higher on high sodium diet than on low sodium diet. Thus, the secretion of AVP was shown to be increased in SHR with high sodium intake. The intravenous injection of an AVP antiserum reduced arterial blood pressure substantially. These results suggest that AVP may function as a direct pressor agent in the maintenance of high blood pressure in SHR.
