Changes of the intrinsic heart rate during the onset of renal hypertension.
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.
Department of Physiology, School of Medicine, Ribeirão Preto, University of São Paulo, Brazil.
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Machado
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Krieger
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Salgado
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D003714:Denervation; D006339:Heart Rate / Q000187:drug effects; D006977:Hypertension, Renal / Q000150:complications / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D013564:Sympathetic Nervous System / Q000503:physiopathology; D013610:Tachycardia / Q000209:etiology / Q000503:physiopathology*
D000804:Angiotensin II; D007545:Isoproterenol; D009638:Norepinephrine