Influence of high dietary sodium intake on the functional subtypes of α1-adrenoceptors in the renal cortical vasculature of Wistar–Kyoto rats

Abstract

1 Increased renal vascular resistance is one renal functional abnormality that contributes to hypertension, and α₁-adrenoceptors play a pivotal role in modulating this renal vascular resistance. This study investigates the functional contribution of α₁-adrenoceptor subtypes in the renal cortical vasculature of Wistar–Kyoto rats on a normal sodium diet (WKYNNa) compared with those given saline to drink for 6 weeks (WKYHNa).

2 The renal cortical vascular responses to the adrenergic agonists noradrenaline (NA), methoxamine (ME) and phenylephrine (PE) were measured in WKYHNa and WKYNNa rats either in the absence (the control phase) or presence of chloroethylclonidine (CEC), an α_1B-adrenoceptor antagonist, 5-methylurapidil (5-MeU), an α_1A antagonist, or BMY7378, an α_1D antagonist.

3 Results showed a greater renal cortical vascular sensitivity to NA, PE and ME in the WKYHNa compared with WKYNNa rats (P < 0.05). Moreover, 5-MeU and BMY7378 attenuated adrenergically induced renal cortical vasoconstriction in WKYHNa and WKYNNa rats; this response was largely blunted in CEC-treated WKYHNa rats (all P < 0.05) but not in CEC-treated WKYNNa rats.

4 The data suggest that irrespective of dietary sodium content, in Wistar–Kyoto rats α_1A- and α_1D-subtypes are the major α₁-adrenoceptors in renal cortical vasculature; however, there appears to be a functional involvement of α_1B-adrenoceptors in the WKYHNa rats.