ALTERED RENAL ALPHA-ADRENOCEPTOR DENSITY INDUCED BY PROLONGED NACL AND DOCA ADMINISTRATION IN SPONTANEOUSLY HYPERTENSIVE RATS

This study examines the effects of a 6-week exposure to 1% NaCl in tap water with and without desoxycorticosterone acetate (DOCA) on renal a adrenoceptors and systolic blood pressure (SBP) in spontaneously hypertensive adult rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. On normal sodium intake, SHR had higher renal α1- (p < 0.05) and α2-adrenoceptor densities (p < 0.001) and SBP (p < 0.001) than WKY rats. Although WKY rats given either 1% NaCl, DOCA, or DOCA plus 1% NaCl developed hypertension after 6 weeks of treatment, only 1% NaCl administration for the same period produced an increase in the α1-adrenoceptor density when compared to the control (p < 0.001). In SHR, ingestion of 1% NaCl or DOCA plus 1% NaCl increased the already elevated α2-adrenoceptor density (p < 0.001) and SBP even more in this strain after 6 weeks of treatment. Equilibrium dissociation constants (Kd), however, were similar for both classes of receptors in experimental and control rats. The results of this study indicate that only the combination of 1% NaCl in tap water and DOCA administration is effective in accelerating hypertension in adult SHR. On the other hand, in this form of genetic rat hypertension, exaggerated sodium intake with or without DOCA administration could presumably be correlated with the increased renal α2 adrenoceptors observed in these animals. © 1990 Raven Press, Ltd., New York.