RENAL DENERVATION ATTENUATES THE SODIUM RETENTION AND HYPERTENSION ASSOCIATED WITH OBESITY

Recent studies have indicated that obesity is associated with hyperten sion, sodium retention, and increased sympathetic nervous system activ ity. The purpose of this study was to determine the role of renal nerv es in mediating the sodium retention and hypertension associated with obesity. We determined the hemodynamic and renal excretory responses t o a high-fat diet in control (n=6) and bilaterally renal-denervated (n =7) chronically instrumented dogs. After a control period of 8 days, d ogs were placed on a high-fat diet for 5 weeks. In response to a high- fat diet, body weight increased from 19.9 +/- 2.2 to 29.9 +/- 2.4 kg i n the control group and from 21.1 +/- 2.0 to 32.4 +/- 1.9 kg in the bi laterally renal-denervated group. Heart rate increased from 81 +/- 8 t o 113 +/- 7 beats per minute in the control group and from 79 +/- 7 to 103 +/- 8 beats per minute in the bilaterally renal-denervated group. Arterial pressure increased significantly from 95 +/- 2 to 109 +/- 4 mm Hg in the control group. In contrast, 5 weeks of a high-fat diet in the bilaterally renal-denervated group did not significantly increase arterial pressure (which went from 87 +/- 3 to 90 +/- 4 mm Hg). Furth ermore, the decrease in sodium excretion in response to the high-fat d iet was significantly greater in the control group than in the bilater ally renal-denervated group. After 5 weeks of a high-fat diet, cumulat ive sodium retention was 455 +/- 85 mmol in the control group and only 252 +/- 47 mmol in the bilaterally renal-denervated group. Similar in creases in glomerular filtration rate and renal plasma flow occurred i n both groups in response to the high-fat diet. The results of this st udy indicate that the renal nerves play an important role in mediating the sodium retention and hypertension associated with obesity in dogs .