Factors Determining the Concentrations of Lysolecithin in Plasma and Tissues

Abstract

Lysolecithin concentrations in the aortic intima plus inner media are greatly increased with atherosclerosis in squirrel monkeys, and with the associated hyperlipemia more than half of plasma lysolecithin is found in the lipoproteins. To explain these findings we studied the metabolism of lysolecithin labeled with [ l-14C]-palmitate and [Me-3H]-choline in vivo in squirrel monkeys and in vitro in aortas of squirrel monkeys and rabbits. The binding in vitro of lysolecithin tdplasma proteins and lipoproteins, as well as to tissue fractions, was also measured. Plasma lysolecithin rapidly entered all tissues including the brain and was directly acylated or hydrolyzed. The H20-soluble products of lysolecithin hydrolysis were present in some tissues but not in others such as the aortic wall. Glycerol phosphorylcholine diesterase appeared to be absent from the aorta. Lysolecithin uptake by the intima plus inner media was greatly increased by atherosclerosis, but the fractional turnover was reduced. The rate of total body production of lysolecithin by the action of LCAT and phospholipases was increased with hyperlipemia. Lysolecithinbinding capacities and affinities of all lipoprotein classes of plasma were much greater than those of albumin. Amongst subfractions from tissue homogenates, the plasma membrane held the most attraction for lysolecithin.