| Abstract: | This study was designed to determine whether verapamil protects renal function in experimental ischemia in the rat and, if so, whether the protection is mediated by verapamil's vasodilatory action or by an effect on renal cells independent of vascular perfusion. Inulin clearance (CIn) was examined for 3 h subsequent to 40 min of unilateral intrarenal infusion of norepinephrine (0.75 microgram X kg-1 X min-1) and 3 and 48 h subsequent to 40 min of unilateral renal pedicle clamp. In norepinephrine-induced ischemia CIn fell to 0.8 +/- 0.4% of preischemic values in saline-treated kidneys and 0.5 +/- 0.3% in verapamil post-treated kidneys. By contrast, CIn fell only to 52.3 +/- 6.5% of preischemic values in verapamil-pretreated kidneys. Verapamil pretreatment significantly counteracted the intrarenal vasoconstriction produced by norepinephrine, sustaining renal blood flow during the norepinephrine infusion. In pedicle clamp-induced ischemia verapamil pre- and posttreatment had no beneficial effect on preservation of glomerular filtration rate, whereas mannitol pretreatment was beneficial. Parallel studies in the isolated perfused rat kidney confirmed the in vivo observations. In conclusion, verapamil exerts no protective effect on renal function at 3 or 48 h when ischemia is induced by renal pedicle clamp. Likewise, verapamil administration subsequent to norepinephrine-induced ischemia is ineffective in preserving renal function. Verapamil pretreatment in norepinephrine-induced ischemia preserves renal function probably by attenuating the vasoconstrictive ischemic insult due to norepinephrine.(ABSTRACT TRUNCATED AT 250 WORDS) |
