Distribution of lecithin-retinol acyltransferase activity in different types of rat liver cells and subcellular fractions

Abstract

It is now well documented that lecithin-retinol acyltransferase (LRAT) is the physiologically important enzyme activity involved in the esterification of retinol in the liver. However, no information regarding the cellular distribution of this enzyme in the liver is presently available. This study characterizes the distribution of LRAT activity in the different types of rat liver cells. Purified preparations of isolated parenchymal, fat-storing, and Kupffer + endothelial cells were isolated from rat livers and the LRAT activity present in microsomes prepared from each of these cell fractions was determined. The fat-storing cells were found to contain the highest level of LRAT specific activity (383 ± 54 pmol retinyl ester formed min −1·mg −1 versus 163 ± 22 pmol retinyl ester formed min −1·mg −1 for whole liver microsomes). The level of LRAT specific activity in parenchymal cell microsomes (158 ± 53 pmol retinyl ester formed min −1-mg −1) was very similar to LRAT levels in whole liver microsomes. The Kupffer + endothelial cell microsome fractions were found to contain LRAT, at low levels of activity. These results indicate that the fat-storing cells are very enriched in LRAT but the parenchymal cells also possess significant levels of LRAT activity.