Endothelin-induced renal vasoconstriction and increase in cytosolic calcium in renal vascular smooth muscle cells.

This study was designed to investigate the effects of the potent vasoconstrictor, endothelin, on renal hemodynamics in rats in vivo, and in addition, to measure intracellular calcium ion ([Ca2+]i) in monolayers of renal vascular smooth muscle cells in culture using the fura-2 method. Endothelin (1 nmol) dramatically decreased renal blood flow from 7.0 +/- 0.5 ml/min to 2.6 +/- 1.0 ml/min, whereas it increased mean arterial pressure from 100 +/- 2 mmHg to 113 +/- 7 mmHg. These alterations persisted over 20 minutes in conscious and almost unrestrained rats. Endothelin (10(-8)-10(-7) mol/l) immediately increased [Ca2+]i, although the increase by endothelin (10(-9) mol/l) was relatively slow. The increase persisted in the presence of 1 mmol/l extracellular calcium. In the absence of extracellular calcium, only a small, transient increase of [Ca2+]i was observed. These results indicate that endothelin produces renal vasoconstriction and increases the [Ca2+]i in cultured renal vascular smooth muscle cells. The latter effect is dependent mainly on extracellular calcium.