CALCIUM CELLS FROM SNAILS - RESPONSE TO VITAMIN-D METABOLITES

Calcium is one of the most important substances affecting the life of molluscs, and vitamin D was shown to be an essential nutrient for land snails. In an attempt to elucidate the role that vitamin D plays in calcium metabolism of land snails, we have developed a procedure for the isolation of specialized calcium cells from digestive gland of land snails, and were able to culture these cells. The effect of vitamin D metabolites on the intracellular exchangeable calcium and alkaline phosphatase activity was studied. The metabolites tested were 25-hydroxycholecalciferol (25(OH)D-3), 24,25-dihydroxycholecalciferol (24,25(OH)(2)D-3), 1,25-dihydroxycholecalciferol (1,25(OH)(2)D-3), and the molluscan metabolite E. 25(OH)D-3 was found to be the most active sterol in elevating intracellular exchangeable calcium and the activity of alkaline phosphatase, and the molluscan metabolite E was found to be the most potent sterol in the suppression of alkaline phosphatase activity. 1,25(OH)(2)D-3 was shown to suppress both activities at high concentrations, and 24,25(OH)(2)D-3 increased the intracellular exchangeable calcium only at high concentrations. Thus, 25(OH)D-3 which is regarded as a storage form of vitamin D and devoid of biological activity, seems to be biologically active in invertebrates.