Calcium deficiency modifies polyunsaturated fatty acid metabolism in growing rats

Fatty acid desaturase activities were determined in liver microsomes from c alcium-deficient rats and compared to calcium-sufficient ones. The calcium- deprived diet (0.5 g/kg) administered for 60 d caused a 30% inhibition in t he Delta 5 desaturase activity and a 45-55% decrease in Delta 6 and Delta 9 , respectively, facts that cannot be attributed to a reduction in food inta ke. In vitro addition of calcium, ethyleneglycol-bis(beta-aminoethyl ether) N,N-tetraacetic acid, and/or cytosol fractions from control or calcium-defi cient rats to microsomes from both groups of animals indicates that the red uced desaturase capacities would be the consequence of an indirect effect o f calcium deprivation. The present work shows that the reduced unsaturated fatty acid biosynthesis might be the result of modifications in the physico chemical properties of microsomal membranes. Such changes could also be der ived from the inhibition of phospholipase A(2) activity induced by calcium deficiency.