RENAL NERVES CONTRIBUTE TO SALT-INDUCED HYPERTENSION IN SINOAORTIC-DENERVATED UNINEPHRECTOMIZED RABBITS

The objective of this study was to investigate the role of the renal nerves in the pathogenesis of salt-induced hypertension in sinoaortic-denervated uninephrectomized rabbits. Twelve rabbits were divided into two groups. Sinoaortic-denervated uninephrectomized rabbits with intact renal nerves (sham group: n = 6) and without renal nerves (RDN group: n = 6). In both groups, 2 days of 154 meq/l NaCl loading was followed by 10 days of 1,700 meq/l NaCl loading. We administered 154 meq/l or 1,700 meq/l NaCl intravenously at every 8 h. Serial changes in mean arterial pressure (MAP) and heart rate (HR) were recorded using a microcomputer system. We chronologically measured hematocrit, serum osmolality, serum sodium, potassium, and chloride concentration, serum creatinine, plasma renin activity, plasma aldosterone, plasma norepinephrine, plasma arginine vasopressin, and plasma atrial natriuretic peptide. Urine volume and body weight were recorded every day, as were urinary concentrations of sodium, potassium, and chloride. The basal value of MAP in the sham group was significantly higher than that in the RDN group (on day -2, 111 +/- 1 mmHg for sham, 99 +/- 2 for RDN, P < 0.001). Hypertonic saline loading induced an elevation of blood pressure in the sham group (126 +/- 2 mmHg on day 4, 127 +/- 2 on day 7, 124 +/- 4 on day 10). There were no significant changes in the response to salt loading in the RDN group. In the sham group, the retention of sodium was significant compared with that in the RDN group on day 5, and this difference was maintained until the end of the experiments. In the sham group, plasma norepinephrine increased twofold on day 4 and decreased gradually (340 +/- 30 pg/ml on day -2, 780 +/- 130 on day 4), and plasma arginine vasopressin increased about threefold from day 1 and maintained (2.4 +/- 0.3 pg/ml on day -2, 5.8 +/- 0.6 on day 1). In the RDN group, there were no significant changes in both hormones in response to salt loading. These results imply that renal nerves contribute to salt-induced hypertension in sinoaortic-denervated rabbits, probably through the combination of several factors such as the retention of sodium, activation of the sympathetic nervous system, and the elevation of plasma arginine vasopressin.