FINE STRUCTURAL LOCALIZATION OF ACYLTRANSFERASE ACTIVITY IN RAT HEPATOCYTES

Abstract

A method for the fine structural localization of acyltransferases catalyzing the transfer of acyl groups from palmityl-coenzyme A (CoA) to α-glycerophosphate based on the formation of a heavy metal precipitate at the site of CoA release is described. In this method CoA released through the action of the enzyme is oxidized by potassium ferricyanide, which is reduced to potassium ferrocyanide and precipitates in the presence of cupric ions. Acyltransferase activity was found to survive both fixation in glutaraldehyde and incubation in the presence of the capture reagent system used for cytochemistry. Reaction product marking the enzyme activity was located within the cisternae of the rough endoplasmic reticulum and to lesser, but significant extent, within the membranous envelope of the smooth endoplasmic reticulum. Reaction product was not associated to any significant extent with other membranous organelles. The significance of these observations in terms of the role of acyltransferases in liver function is discussed.