Changes of the Intrinsic Heart Rate During the Onset of Renal Hypertension

Abstract

Intrinsic heart rate (IHR) measured after autonomic blockade with atropine and propranolol in conscious one-kidney, one clip (1-K,1C) hypertensive rats was increased and associated with the peak of tachycardia that occurs 7 days after clipping. No significant changes in basal or intrinsic heart rate were observed 3 or 14 days after clipping. The effect of exogenous angiotensin II (ANG II) was compared to that of norepinephrine (NOR) and isoproterenol (ISO) in conscious normotensive rats. Infusion of ANG II for 3 h induced a slight increase in heart rate which was accompanied by a larger increase in IHR. In contrast, the infusion of NOR or ISO induced intense tachycardia without affecting IHR. The intense tachycardia observed in conscious rats 48 h after sinoaortic denervation, was not accompanied by changes in IHR. Furthermore, the adrenergic stimulation produced by infusion of either NOR or ISO or that occurring after 48 h of sinoaortic denervation, did not modify IHR in conscious rats, whereas a 3-h infusion of ANG II did. These data suggest that the tachycardia observed in rats during the onset of 1-K,1C hypertension may be partly due to increased IHR caused by ANG II.