EFFECT OF WEIGHT-REDUCTION IN MODERATELY OVERWEIGHT PATIENTS ON RECORDED AMBULATORY BLOOD-PRESSURE AND FREE CYTOSOLIC PLATELET CALCIUM

Although platelet cytosolic calcium has been shown to decrease during pharmacological treatment of hypertension, there is no evidence that cytosolic calcium also falls during a nonpharmacological reduction in blood pressure. To provide such evidence, we examined prospectively the relation between platelet cytosolic calcium and ambulatory blood pressure during weight reduction in moderately overweight (body mass index [BMI] > 25), mildly hypertensive individuals. The experimental group ( responders: BMI reduction > 5%) consisted of 19 patients who lost 8.5 +/- 2.9 kg (mean +/- SD, p < 0.05) during a 10-week hypocaloric diet, whereas the control group (nonresponders: BMI reduction < 5%) consisted of 12 patients who showed no relevant change in body weight (-2.0 +/- 1.3 kg) during the same period of time. The moderate weight loss of the responders decreased blood pressure by 14/5 mm Hg (p < 0.05), as measured by ambulatory monitoring, which renders a placebo effect unlikely. This nonpharmacological reduction in blood pressure was accompanied by a proportional 11% decrease (p < 0.05) in platelet cytosolic calcium and also by significant (p < 0.05) decreases in plasma catecholamines and serum cholesterol. These findings establish the concept of a nonpharmacological reduction in free cytosolic platelet calcium in humans and add further evidence suggesting a link between intracellular calcium homeostasis and blood pressure regulation.