Baroreflex Sensitivity in Rabbits During the Development of Experimental Renal Hypertension and Medial Sclerosis

Abstract

Baroreflex sensitivity was assessed in 9 normotensive (N), 8 renal wrap (1 kidney model, RH) and 16 medial sclerotic rabbits (MS, fed on calciferol 50,000 IU and calcium lactate 1 g for 10 days) before (mean BP [blood pressure]; N, 79 .+-. 3.3 mm Hg; RH, 80 .+-. 7.4 mm Hg; and MS, 83 .+-. 1.0 mm Hg) and at monthly intervals for up to 16 wk after induction of the disease processes (mean BP; N, 87 .+-. 3.9 mm Hg; RH, 127 .+-. 7.2 mm Hg and MS, 99 .+-. 3.8 mm Hg). BP was elevated by i.v. phenylephrine (5 and 10 .mu.g/kg) or angiotensin (250 ng/kg) and baroreflex sensitivity assessed by the increase of pulse interval per unit rise of pressure. The pressor response was greater in the RH and MS than in the N rabbits. The baroreflex sensitivity showed a progressive reduction with time and with the elevation of BP in MS and RH rabbits. The difference was significantly greater (P < 0.01) than in the age-related control rabbits (P > 0.05). There was an inverse relationship between baroreflex sensitivity and the pressor response in MS rabbits. Progressive baroreceptor dysfunction is indicated in hypertensive and medial sclerotic rabbits.