ROLE OF SYMPATHETIC ACTIVITY IN BLOOD-PRESSURE REDUCTION WITH LOW CALORIE REGIMEN

To investigate the effects of a low calorie regimen on sympathetic function and its relation to blood pressure response, 22 untreated obese essential hypertensive patients (50 +/- 2 years, body mass index 29 +/- 1 kg/m2) were hospitalized and a diet was prescribed of 2,000 kcal/day for 5 days (control period) followed by 800 kcal/day for 21 days without changing salt intake (8-10 g/day). The dose of intravenous phenylephrine infusion needed to elevate systolic blood pressure 20 mm Hg (CD20) and the 24-hour urinary excretion of norepinephrine (U(NE)) were measured. During the low calorie period, blood pressure normalized in 14 patients (responder group, 124 +/- 3/79 +/- 4 mm Hg) and eight remained hypertensive (poor responder group, 158 +/- 6/103 +/- 3 mm Hg). At the control period, blood pressure and body mass index were similar, but the responder group had higher U(NE) (134 +/- 15-mu-g/day) and CD20 (127 +/- 11-mu-g) than the poor responder group (89 +/- 6-mu-g/day and 79 +/- 13-mu-g, respectively). During the low calorie period, both U(NE) (87 +/- 15-mu-g/day) and CD20 (74 +/- 10-mu-g) decreased in the responder group; no change was seen in the poor responder group. Changes in U(NE) and systolic blood pressure were correlated (r = 0.6, p < 0.05). In conclusion, suppression of sympathetic activity plays a role in blood pressure reduction during moderate caloric restriction.