Atrial stretch-induced diuresis in Brattleboro rats

Inflation of a balloon at the superior vena caval/right atrial junction of the conscious Brattleboro rat initiated a rapid and significant diuresis, natriuresis, and kaliuresis (urine volume increased from 20.8 +/- 0.8 to 28.5 +/- 1.3 ml/h, P less than 0.005; urine sodium increased from 2,417 +/- 115 to 3,510 +/- 230 mu eq/h, P less than 0.005; urine potassium increased from 351 +/- 52 to 478 +/- 58 mu eq/h, P less than 0.05; n = 6). Bilateral renal denervation did not significantly alter this response. Since the Brattleboro rat is totally deficient in antidiuretic hormone (ADH) and since inflation of the balloon causes no change in blood pressure, the reflex increase in urinary salt and water output must be mediated, at least in part by a blood-borne factor other than ADH.