ROLE OF CALCIUM-CHANNEL BLOCKERS IN PREVENTING ACUTE AND CHRONIC RENAL INJURY

Calcium-channel blockers (CCBs) have been shown to afford protection against acute (ARF) and chronic renal failure (CRF). The effects of CCBs against acute renal injury occur at both the vascular and tubular epithelial level. At the vascular level, experimental ARF-associated loss of renal autoregulation and hypersensitivity to renal nerve stimulation has been shown to be reversed by CCBs. These beneficial vascular effects of CCBs occur on the background of the finding that renal ischemic injury is associated with an increase in cellular Ca2+ concentration. A rise in tubular epithelial Ca2+ concentration also occurs very early after a renal ischemic insult. This effect of ischemia is associated with evidence of membrane depolarization, opening of slow calcium channels, increased cellular Ca2+ uptake, and reversal by CCBs. There is evidence that the increased cellular Ca2+ uptake activates phospholipases, which prolong and increase membrane damage. Experimental CRF is also associated with increased renal cellular Ca2+ concentration, an effect that can be attenuated by CCBs. The CCBs probably slow progression of CRF by both cytoprotective and antihypertensive effects. These findings of vascular and tubular effects of CCBs in experimental ARF and CRF have led to their clinical use to prevent initial dysfunction of cadaveric kidney transplants, cyclosporine nephrotoxicity, radiocontrast-induced ARF, and progression of CRF. Randomized clinical studies are necessary to further examine the efficacy of CCBs in ARF and CRF.