Calcium and phosphorous deficiencies alter the lipid composition and fluidity of intestinal basolateral membranes

Steady-state fluorescence polarization and lipid composition studies were undertaken on intestinal basolateral membranes (BLM) from chicks adapted to a calcium deficient (low Ca) or a phosphorous deficient diet (low P). The fluorescence anisotropy showed that fluidity of intestinal BLM was increased by the mineral deprivations, but the response of the membranes varied with the specific fluorophore used. The "static" component of fluidity, assessed by 1,6-diphenyl-1,3,5-hexatriene (DPH), was increased whereas the "dynamic" component, monitored with DL-12-(9-anthroyloxy)-stearic acid (12-AS), was not modified. Low P diet produced significant changes in lipid composition such as a decrease in the cholesterol content and in the sphyngomyelin (Sph) and phosphatidylserine plus phosphatidylinositol fractions (PS + PI) and increment in the phosphatidylcholine (PC) proportion. The percent of monounsaturated fatty acids was increased by the low P diet due mainly to an increase in the oleic acid fraction. Minor changes such as a decrease in the palmitic acid and increases in the 22:5n3 and 22:6n3 fatty acids were caused by Ca deficiency. The alteration of the biochemical and biophysical membrane properties of the BLM of the mineral deficient groups might play a role in the enhanced intestinal Ca and P absorption.