1,25(OH)2D3 increases membrane associated protein kinase C in MDBK cells

To determine whether 1,25-dihydroxycholecalciferol [1,25(OH)2D3] affects protein kinase C (PKC) activity in kidney, as has been demonstrated in HL-60 cells we measured 1,25(OH)2D3 binding, PKC activity and PKC immunoreactivity in Madin Darby bovine kidney (MDBK) cells, a normal renal epithelial cell line derived from bovine kidney. Our data demonstrate that MDBK cells exhibit specific high affinity binding for 1,25(OH)2D3, indicating the presence of the vitamin D receptor (VDR). Treatment of MDBK cells with 1,25(OH)2D3 for 24 h increased membrane PKC activity and immunoreactivity. The effect of 1,25(OH)2D3 was dose-dependent, with a peak effect observed at 10(-7)M 1,25(OH)2D3. The 1,25(OH)2D3 induced increase in membrane PKC was paralleled by a comparable decrease in cytosolic PKC activity and amount. Although time course studies were consistent with a VDR mediated effect of 1,25(OH)2D3 on PKC protein synthesis, total PKC activity was not increased by 1,25(OH)2D3, suggesting an effect on PKC translocation or localization. These results suggest that 1,25(OH)2D3 modulates PKC mediated events in kidney, a classic target for this steroid hormone.