Summary.-The chronic administration of N-2-acetylaminofluorene (N-2-AAF) to rats causes a loss of hepatic cytoplasmic RNA, particularly from the endoplasmicmembrane fractions. At the end of the complete carcinogenic dose, the level of aminoacid incorporation into proalbumin is normal, despite the loss of 35%0 of membranebound RNA. The secretion of albumin, however, is inhibited. This inhibition of secretion is apparently the result of a change in membrane flow and differentiation; transfer of nascent protein from smooth-surfaced vesicles to the Golgi apparatus is blocked. The significance of these findings is discussed.

Sealed membrane vesicles were prepared from microsomes and glyoxysomes isolated from the endosperm tissue of germinating castor bean. Peripheral-membrane proteins together with soluble protein present in the luminal space of the microsomes or the matrix of the glyoxysomes were released from intact organelles by osmotic shock in the presence of salt. The washed membrane vesicles were linked to cyanogen-bromide-activated Sepharose. Where appropriate, the immobilized vesicles were made permeable to protein molecules by controlled detergent treatment which did not result in significant solubilization of the lipid bilayer. Released luminal proteins were allowed to interact with the membrane vesicles under conditions which gave them access to the cytoplasmic surface only or to both the cytoplasmic and luminal surfaces. While microsomal luminal proteins did not interact with either surface of the membrane vesicles, glyoxysomal matrix proteins specifically bound to the luminal surface of the glyoxysomal membrane. Binding seemed to be effected via the oligosaccharide chains of glyoxysomal membrane glycoproteins since (a) bound proteins could be released by elution with sugar solution, and (b) solubilized glyoxysomal membrane proteins specifically interacted with immobilized lectins.