EFFECT OF CALCIUM AND CELL IMMOBILIZATION ON THE PRODUCTION OF CHOLEOCALCIFEROL AND ITS DERIVATIVES BY SOLANUM MALACOXYLON CELL-CULTURES

Cell suspension cultures of Solanum malacoxylon cultivated in standard B5 medium containing 1 mM CaCl2 accumulated larger amounts of both vi tamin Dg (cholecalciferol) and 25-OH D-3 (25-hydroxycholecalciferol) t han cells in medium containing 10 mM CaCl2. The amount of vitamin D-3 in calcium-free medium was similar to that in standard medium, while t he 25-OH D, level was 50 time greater; 1 alpha,25(OH)(2) D-3 (calcitri ol) was detected only in chloroform extracts of cells cultivated in st andard medium. It was found that immobilized cells accumulated vitamin D, and 25-OH D, for prolonged culture periods (up to 30 days) and wer e able to biotransform vitamin D, when it was supplemented as an exoge nous precursor. S. malacoxylon suspension cell cultures were able to s ynthesize vitamin D-3, 25-OH D-3 and 1 alpha,25(OH)(2)D-3 under differ ent; experimental conditions, therefore suggesting the presence of enz yme systems able to hydroxylate vitamin D, at positions C-25 and C-1. In Solanum malacoxylon, as in animals, the concentration of calcium ma y have an effect on the regulation of vitamin D-3 synthesis and the pr oduction of its hydroxylated metabolites. (C) 1997 Elsevier Science Lt d.