EFFECTS OF ENDOTHELIN-3 ON WATER AND SODIUM-EXCRETION DURING EXTRACELLULAR VOLUME EXPANSION

The aim of the present study was to elucidate the role of an TV dose o f endothelin-3 (ET-3) (5 ng Kg(-1) min(-1)) on mean arterial pressure (MAP), on diuresis and natriuresis in control and in volume expanded a nesthetized rats. A systemic infusion of ET-3 in normal rats (Group I) increased MAP and produced a trend of increasing diuresis, without ch anges in natriuresis, A 10% body weight expansion (Group II) increased diuresis and natriuresis without changes in MAP. The simultaneous inf usion of ET-3 and expansion with saline (Group III) resulted in an inc rease in MAP, an enhanced diuretic response, and a natriuresis of simi lar magnitude to that observed in Group II. These results suggest that the diuresis produced by a low dose of exogenous ET-3 in control rats , is independent of sodium excretion, Furthermore, the enhanced diures is caused by ET-3 during expansion is greater than the addition of ET- 3 and expansion effects, suggesting that new mechanisms are triggered in order to maintain volume and salt homeostasis in this state. (C) 19 98 Elsevier Science Inc.