The Effect of Vitamin D3 Supplementation on Intracellular Calcium and Plasma Membrane Calcium ATPase Activity in Early Stages of Chronic Kidney Disease

Chronic kidney disease (CKD) is associated with increased concentration of intracellular calcium, which is pathological and may lead to irreversible damage of cell functions and structures. The aim of our study was to investigate the impact of 6 months vitamin D-3 supplementation (14 000 IU/week) on free cytosolic calcium concentration ([Ca2+](i)) and on the plasma membrane calcium ATPase (PMCA) activity of patients with CKD stage 2-3. PMCA activity of patients was also compared to that of healthy volunteers. Vitamin D-3 supplementation of CKD patients resulted in the decrease of [Ca2+](i) (119.79 +/- 5.87 nmol/l vs. 105.36 +/- 3.59 nmol/l, n=14, P<0.001), whereas PMCA activity of CKD patients (38.75 +/- 22.89 nmol Pi/mg/h) remained unchanged after vitamin D-3 supplementation (40.96 +/- 17.74 nmol Pi/mg/h, n=14). PMCA activity of early stage CKD patients before supplementation of vitamin D-3, was reduced by 34 % (42.01 +/- 20.64 nmol Pi/mg/h) in comparison to healthy volunteers (63.68 +/- 20.32 nmol Pi/mg/h, n=28, P<0.001). These results indicate that vitamin D-3 supplementation had a lowering effect on [Ca2+](i) and negligible effect on PMCA activity in CKD patients.