Plasma renin activity (renin) and hemodynamic response to venous pooling of blood in legs were studied in 24 healthy volunteers and four patients who after bilateral nephrectomy received a functioning renal transplant. Blood pressure cuffs were placed around subjects' thighs and inflated at a pressure 5 mm Hg below the individuals' diastolic pressures. 30 min after thigh cuff inflation, renin significantly increased in all volunteers (mean = 125%). Inflation of cuffs induced a decrease of right atrial pressure, cardiopulmonary blood volume, and cardiac output, but there were no changes in the extra-arterial systolic and diatoloic pressure or in the pressure amplitude. After cuffs were deflated, renin and hemodynamic parameters returned toward normal. In nine volunteers in whom thigh cuff inflation initially elicited renin increases, subsequent intravenous propranolol (0.25 mg/kg) abolished the response to repeated cuff inflation. The renin increase to thigh cuff inflation was absent or suppressed in four patients with a recently transplanted denervated kidney. It is concluded that thigh cuff inflation elicited a reflex-mediated renin increase, and that the reflex stemmed from stimulation of cardiopulmonary mechanoreceptors.
W Kiowski, S Julius