Effect of renal ischemia on cortical microsomal calcium accumulation

Mitochondrial respiration, Ca²⁺ content, and Ca²⁺ kinetics have been found to be profoundly altered in ischemic acute renal failure (ARF). The effect of clamping the bilateral renal artery for 50 and 90 min on microsomal Ca²⁺ uptake was therefore examined in the rat. The 50-min clamping produced a reversible model of nonoliguric ARF, and the 90-min clamping produced a model of nonreversible oliguric ARF. In the 50-min nonoliguric model, ATP-dependent Ca²⁺ uptake by microsomes from renal cortex (nmol·mg protein^-1·30 min^-1) was significantly impaired immediately before release of the clamp and before return of renal blood flow (reflow) (191 ± 11 vs. 83 ± 11, P < 0.005). However, in this nonoliguric model of ischemic ARF, microsomal uptake returned completely to normal after 1 h of reflow (sham 189 ± 11 vs. 167 ± 14 at 1 h, NS) and persisted at this normal level at 24 h (sham 166 ± 14 vs. 150 ± 13 at 24 h, NS). In the oliguric model of ARF the microsomal Ca²⁺ uptake also was impaired immediately after the clamp release (sham 191 ± 11 vs. 93 ± 11, P < 0.001) as well as after 1 h of reflow (sham 189 ± 11 vs. 129 ± 12, P < 0.005) but not at 24 h (sham 166 ± 14 vs. 173 ± 13, NS). The results indicate that impaired microsomal Ca²⁺ uptake occurs early in both oliguric and nonoliguric ARF and persists after 1 h of reflow in the oliguric model. However, after 24 h of reflow in models of ARF, no evidence of impaired microsomal Ca²⁺ uptake was observed.