Prolonged Baroreflex Activation Abolishes Salt-Induced Hypertension After Reductions in Kidney Mass

Chronic electric activation of the carotid baroreflex produces sustained reductions in sympathetic activity and arterial pressure and is currently being evaluated for therapy in patients with resistant hypertension. However, patients with significant impairment of renal function have been largely excluded from clinical trials. Thus, there is little information on blood pressure and renal responses to baroreflex activation in subjects with advanced chronic kidney disease, which is common in resistant hypertension. Changes in arterial pressure and glomerular filtration rate were determined in 5 dogs after combined unilateral nephrectomy and surgical excision of the poles of the remaining kidney to produce approximate to 70% reduction in renal mass. After control measurements, sodium intake was increased from approximate to 45 to 450 mol/d. While maintained on high salt, animals experienced increases in mean arterial pressure from 102 +/- 4 to 121 +/- 6 mmHg and glomerular filtration rate from 40 +/- 2 to 45 +/- 2 mL/min. During 7 days of baroreflex activation, the hypertension induced by high salt was abolished (103 +/- 6 mmHg) along with striking suppression of plasma norepinephrine concentration from 139 +/- 21 to 81 +/- 9 pg/mL, but despite pronounced blood pressure lowering, there were no significant changes in glomerular filtration rate (43 +/- 2 mL/min). All variables returned to prestimulation values during a recovery period. These findings indicate that after appreciable nephron loss, chronic suppression of central sympathetic outflow by baroreflex activation abolishes hypertension induced by high salt intake. The sustained antihypertensive effects of baroreflex activation occur without significantly compromising glomerular filtration rate in remnant nephrons.