Sexual dimorphism of renal α2-adrenergic receptor regulation in Dahl rats

Abstract

Male Dahl salt-sensitive hypertensive (S) rats develop hypertension faster than females. We measured renal α2-adrenergic receptor density of inbred Dahl salt sensitive (SS/JR) and salt-resistant (SR/JR) rats, using [3H]-rauwolscine saturation binding studies. Male and female SS/JR rats were gonadectomized or sham-operated at 6 weeks of age and fed a high salt diet for 4 weeks. Additional intact SS/JR and SR/JR rats of both sexes were fed the high salt diet for a longer period of time (7 weeks instead of 4 weeks). Both blood pressure and renal α2-adrenergic receptor density were significantly higher in male than female SS/JR rats on high salt diet for 4 weeks. Gonadectomy did not change blood pressure nor did it change renal α2-adrenergic receptor density measured at the 4th week of high salt feeding in either male or female SS/JR rats. When the SS/JR rats were fed high salt diet for a longer period (for 7 weeks), blood pressure of female SS/JR reached the level of males, but the density of renal α2-adrenergic receptors was still significantly lower than that of males. Both renal α2-adrenergic receptor density and blood pressure were higher in male than female SR/JR. We conclude that higher blood pressure in male Dahl SS/JR and SR/JR rats is associated with higher renal α2-adrenergic receptor density compared with their female counterparts.