An examination of rat liver smooth endoplasmic reticulum membranes for the presence of associated messenger RNA

Abstract

Smooth endoplasmic reticulum membranes were isolated from rat hepatocytes and compared with rough endoplasmic reticulum in terms of the types of RNA present. Smooth endoplasmic reticulum membranes contained only 20% the amount of ribosomes per gram equivalent liver as did rough endoplasmic reticulum membranes. Furthermore, the ribosomes were only about 33% as active per mg RNA in the incorporation of [ 3H]leucine using an in vitro protein synthesizing system. Per gram equivalent, smooth endoplasmic reticulum membranes exhibited only 20% the amount of poly(A) associated with rough endoplasmic reticulum membranes and, in contrast to the situation for rough endoplasmic reticulum, most of this poly(A) was removed by treatment with high salt and puromycin. No evidence for the presence of untranslated messenger RNA was found in either rough or smooth endoplasmic reticulum preparations.