Regulation of osteopontin expression in a rat model of urolithiasis.

OBJECTIVE

To investigate the relationship between the expression and regulation of osteopontin (OPN) and urolithiasis.

METHODS

Normal and stone model rats were treated with 1,25-dihydroxyvitamin D3(D3), vitamin K, testosterone or estradiol for 7 days, and the expression of osteopontin and its mRNA were detected with immunohistochemistry and Northern blot, respectively. Crystals deposited in rat kidneys were observed with a polarization microscope. The concentrations of crystal components in rat urine were determined.

RESULTS

The results showed that vitamin K, testosterone and estradiol up-regulated the expression of OPN mRNA and its protein, thus decreasing the precipitation of calcium oxalate in rat kidneys. D3 increased the concentration of calcium in urine, and accelerated the sedimentation of calcium oxalate in rat kidneys.

CONCLUSIONS

These findings indicate that OPN may be an important macromolecule in the normal endogenous inhibition of the formation of urolithiasis. Vitamin K, testosterone and estradiol inhibit the formation of stones via up-regulating the expression of OPN in kidneys, while D3 over dose may accelerate the process.