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

Baroreflex sensitivity was assessed in 9 normotensive (N), 8 renal wrap (one kidney model, RH) and 16 medial sclerotic rabbits (MS, fed on calciferol 50,000 i.u. and calcium lactate 1g for 10 days) before (mean BP;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 weeks after the 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). Blood pressure was elevated by i.v. phenylephrine (5 and 10 micrograms.kg-1) or angiotensin (250 ng.kg-1) 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 blood pressure in both MS and RH rabbits. The difference was significantly greater (P < 0.01) than in the aged related control rabbits (P < 0.05). There was an inverse relationship between baroreflex sensitivity and the pressor response in MS rabbits. Results indicated progressive baroreceptors dysfunction in hypertensive and medial sclerotic rabbits.