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Calcium antagonists and renal hemodynamics: implications for renal protection.

Recently, attention has focussed on the effects of calcium antagonists on renal function. When administered in vitro to the isolated perfused kidney, calcium antagonists exhibit consistent actions permitting characterization of their renal hemodynamic effects. Calcium antagonists do not affect the vascular tone of the vasodilated isolated perfused kidney, but they do dramatically reverse the response of this preparation to vasoconstrictor agents. Studies using the isolated hydronephrotic rat kidney model, which permits direct visualization of afferent and efferent arterioles, have demonstrated that calcium antagonists selectively vasodilate preglomerular vessels. The clinical implications of such observations are still being delineated. Nevertheless, the results of preliminary studies in experimental animal models and in human transplant recipients suggest that calcium antagonists exert salutary effects on renal function in clinical settings characterized by impaired renal hemodynamics. Furthermore, a case can be made that these salutary renal hemodynamic effects of calcium antagonists commend their use in the management of essential hypertension.