CALCIUM-TRANSPORT BY ISOLATED BRUSH-BORDER AND BASOLATERAL MEMBRANE-VESICLES - ROLE OF ESSENTIAL FATTY-ACID SUPPLEMENTATION

Intestinal calcium transport is important in whole body calcium homeostasis and it is therefore of interest to understand the mechanism of absorption and its regulation by 1;25dihydroxyvitamin D-3 (1,25 (OH)(2)D-3) (vitamin D). Significant changes in lipid composition of membranes have previously been shown in response to vitamin D-3 administration. Deficiency in essential fatty acids (EFAs) may influence the vitamin D-dependent calcium absorption in the intestinal tract. The purpose of this study was to investigate the effect of unsaturated fatty acid supplementation on calcium transport. Simultaneous measurements of calcium transport, membrane fluidity and lipid structure have rarely been performed on the same preparation. Intestinal membrane vesicles were prepared using a novel procedure. Vesicles prepared from fish oil and evening primrose oil supplemented animals revealed the highest calcium transport over time as well as the highest degree of unsaturation as compared to those from animals which were unsupplemented or given sunflower or coconut oil. The relative content of polyunsaturated fatty acids in the intestinal membranes may change fluidity, enhance calcium transport and may influence the action of vitamin D-3 on calcium absorption.