Hypertensinogenic factors and renal α-adrenoceptors in young SHR and WKY rats

Abstract

The effects of high sodium intake (drinking 1% NaCl), DOCA and DOCA + 1%NaCl for 6 weeks on renal α 1- and α 2- adrenoceptors and on systolic blood pressure (SBP) were examined in young spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). On normal sodium intake, SHR rats had higher renal α 1 (p < .001) and α 2- adrenoceptor densities (p < .001) and SBP (p < .001) than WKY rats. Although, WKY rats given either 1% NaCl, DOCA, and DOCA + 1% NaCl developed hypertension after 6 weeks of treatment, only 1% NaCl administration for the same period produced an increase in the α 1- and α 2-adrenoceptor densities when compared to the control (p < .01 and p < .001, respectively). In the SHR rats, to the contrary, ingestion of 1% NaCl and DOCA + 1% NaCl increased the already elevated α 2-adrenoceptor density (p < .001) and SBP even more in this strain after 6 weeks of treatment. Equilibrium dissociation constants (K D), however, were similar for both classes of receptors in experimental and control rats. This study indicates that postweaning exposure of the WKY and SHR rats to a high salt treatment and DOCA can influence the renal α-adrenoceptor densities. Although the functional significance of the changes is unclear, it is reasonable to speculate that postweaning exposure to a hypertensinogenic stimuli such as a 1% NaCl and/or DOCA may ultimately interfere with the functional development of the kidney differently in rats genetically predisposed to hypertension (SHR) from normotensive (WKY) rats.