Abstract:

Objective To investigate the effects of hyperoxaluria on rat renal tubular epithelium intracellular calcium concentration ([Ca²⁺]i) and cell apoptosis, and explore the protective effects of calcium antagonist-nifedipine. Methods Sixty male SD rats were randomly divided into six groups (n=10). Rats in water-drinking group were treated with deionized water, nifedipine group with deionized water and nifedipine 10 mg·kg^-1·d^-1, calculiinduced group with deionized water containing 1% ethylene glycol, and three calculi-induced+nifedipineintervening groups with deionized water containing 1% ethylene glycol plus nifedipine 3, 6 and 10 mg·kg^-1·d^-1, respectively. Four weeks later, the 24 h oxaluria concentration was measured, the apoptosis index of renal tubular epithelial cells was detected with TUNEL method, and Ca²⁺ fluorescence intensity of cells of renal proximal tubules was determined by flow cytometry using Fluo-3/AM staining. Results The 24 h oxaluria concentrations in calculi-induced group and calculi-induced+nifedipine-intervening groups were higher than those in water-drinking group and nifedipine group （P＜0.01）. The apoptosis index and Ca²⁺ fluorescence intensity were significantly higher in calculi-induced group than those in water-drinking group （P<0.01）. The Ca²⁺ fluorescence intensity in calculi-induced+nifedipine (3, 6 and 10 mg·kg^-1·d^-1)-intervening groups was 76.7％, 62.7％ and 56.4％ of calculi-induced group, respectively, with a significant dose-effect relationship (r=0.839, P<0.01). The apoptosis index of renal tubular epithelial cells was significantly correlated with Ca²⁺ fluorescence intensity (r=0.826, P<0.01). Conclusion Hyperoxaluria can increase apoptosis and \[Ca2+\]i concentration of renal tubular epithelial cells in rats, and nifedipine can effectively protect renal tubular epithelial cells to resist hyperoxaluria.

Key words: kidney, oxalate, calcium, apoptosis, nifedipine