Modulation of calcium homeostasis and ATPase activity in erythrocyte membrane of patients afflicted with fluorosis

The present study was performed to evaluate effect of consumption of excessive fluoride in drinking water by individuals on erythrocyte membrane activity of Ca 2+ -ATPase and its transport mechanism of Ca 2+ ions. Areas with different fluoride concentration in drinking water were divided into five study groups viz; Control (0.63-1.00 mg/L), A-I (8.00-10.00 mg/L), A-II (10.01-12.00 mg/L), A-III (12.01-14.00 mg/L) and A-IV (14.01-16.00 mg/L). Erythrocytes were used for the estimation of intra-erythrocyte calcium concentrations. Serum samples were analysed for fluoride content. Ca 2+ -ATPase activity was determined spectrophotometrically from ghost erythrocyte membranes. Results showed a significant decrease in intraerythrocyte calcium (F = 50.289, P<0.001) and elevated levels of serum fluoride (F = 9900.90, P<0.001) in fluorotic patients. Regression analysis showed significant negative (P<0.001) relationship of water (r = -0.972, R 2 = 0.945, Y = 0.013 + 0.0001 X) as well as serum fluoride (r = -0.955, R 2 = 0.912, Y = 0.007 + 0.072 X, P<0.001) with intracellular calcium concentrations. Membrane bound Ca 2+ -ATPase activity was noted with highly significant reduction (F = 30819.16, P < 0.001) in patients of fluorosis. Regression analysis exibited significant inverse (P<0.001) relationship of water (r = -0.986, R 2 = 0.973, Y = 0.33 0.01 X) as well as serum fluoride (r = -0.997, R 2 = 0.995, Y = 0.34 0.36 X, P<0.001) with erythrocyte membrane Ca 2+ -ATPase activity. These findings suggest that depression of erythrocyte Ca 2+ ions and Ca 2+ -ATPase pump has been implicated in the pathogenesis of membrane abnormalities observed in fluorotic patients.