Diltiazem and renal hemodynamics: implications for renal protection.

During the past decade, attention has focused on the effects of calcium antagonists on renal function. When administered in vitro to the isolated perfused kidney, calcium antagonists (including diltiazem) do not affect the vasodilated isolated perfused kidney, but they do dramatically alter the response of this preparation to vasoconstrictor agents. Our recent studies using the isolated perfused hydronephrotic rat kidney model, which permits direct visualization of afferent and efferent arterioles, have demonstrated that the preferential augmentation of glomerular filtration rate induced by calcium antagonists in the isolated perfused kidney is attributable to preferential vasodilation of preglomerular vessels. Although the clinical implications of such observations have not been fully delineated, the results of recent studies indicate that calcium antagonists exert salutary effects on renal function in patients with impaired renal hemodynamics, such as radiocontrast-induced nephrotoxicity and transplant-associated acute renal insufficiency.