[Effects of human atrial natriuretic factor-(99-126) on plasma and brain vasopressin in stroke-prone spontaneously hypertensive rats].

In order to investigate the interaction between atrial natriuretic factor (ANF) and arginine vasopressin (AVP) in the pathogenesis of essential hypertension, the effects of intravenous (iv) or intracerebroventricular (icv) injection of human ANF-(99-126) on plasma and brain AVP, as well as mean arterial pressure (MAP), urinary volume (UV) and sodium (UNaV) excretion in stroke-prone spontaneously hypertensive rats (SHRsp) and age-matched normotensive Wistar-Kyoto rats (WKY) were studied. The results showed that ten minutes after iv injection of ANF, MAP decreased by 9.4% and 12.2% (P less than 0.05), UV increased about 9 and 20 folds (P less than 0.01), UNaV increased about 16 and 29 folds (P less than 0.01) in SHRsp and WKY rats, respectively. No such significant changes in these parameters were found in the icv group. Although iv and icv injection of ANF caused significant decrease of plasma AVP in both strains, the decrease was less marked in SHRsp than in WKY rats, while the maximum decreases were 58% (iv) and 31% (icv) in SHRsp, the corresponding values were 80% (iv) and 65% (icv) in WKY. Intravenous and intracerebroventricular injection of ANF also induced significant increase of hypothalamic AVP in both SHRsp and WKY rats, but no significant change could be found in hypophyseal AVP content. The results suggest that decreased sensitivity of AVP inhibition as well as less marked hypotensive, diuretic and natriuretic effects to ANF in SHRsp might play a role in the pathogenesis of their hypertension.