1,25-Dihydroxyvitamin D3 effects in rat kidney: regulation of protein phosphorylation

This study tested the hypothesis that 1,25-dihydroxyvitamin D3 treatment alters the pattern of protein phosphorylation in rat kidney. Treatment with 1,25-dihydroxyvitamin D3 (100 ng/day s.c. x 7d) in vitamin D-deficient rats markedly decreased phosphorylation of a particulate protein (91 +/- 0.6 kDa, n = 9) and moderately increased phosphorylation of a cytosolic protein (108 +/- 0.8 kDa, n = 9) in the kidney. The decreased phosphorylation of the 91-kDa particulate protein showed a graded dose response (0-200 ng/day), as did the more moderate increase in phosphorylation of the 108-kDa cytosolic protein. In conclusion, this study has provided evidence that 1,25-dihydroxyvitamin D3 plays an important role in the regulation of protein phosphorylation in rat kidney and adds these biochemical events to the growing list of 1,25-dihydroxyvitamin D3 effects in this poorly understood target tissue.