Lecithin--cholesterol--acyltransferase activity in the plasma of immature, oestrogenised and laying fowl (Gallus domesticus).

A study was made of the role of the lecithin-cholesterol-acyltransferase (LCAT) enzyme in the changes in the concentrations and fatty acid composition of the plasma cholesteryl esters of the fowl associated with oestrogen treatment and sexual maturity. Although there was a considerable increase in the concentration of free cholesterol in the plasma of oestrogen treated and laying birds, only in the oestrogen treated birds was it associated with an increased rate of cholesterol esterification. In both laying and oestrogen treated birds, changes in the fatty acid composition of the plasma cholesterol esters could be attributed to related changes in the fatty acid specificity of the LCAT enzyme. Evidence is provided to indicate that the cholesterol esters in the plasma of the fowl are synthesised mainly by the plasma LCAT system. The changes in the rates and fatty acid specificity of the LCAT system in the plasma of the fowl associated with sexual maturity or oestrogen treatment are discussed in relation to the extensive alterations shown to occur in the lipoprotein pattern of the plasma.