Immunological Studies of Microsomal Structure 

 and Function 



Peter Perlmann and Winfield S. Morgan* 



The Wenner-Gren Institute for Experimental Biology, 

 University of Stockhohn, Szveden 



In a number of publications it has been shown that specific antibodies 

 can be used as tools for studying the intracellular distribution of anti- 

 genically distinct macromolecules of rat liver [i, 15, 20]. In this paper, the 

 immunological properties of microsomal fractions from various organs 

 will be described, and some of our recent findings will be discussed with 

 regard to microsomal function in protein synthesis. In the present context, 

 the term microsomes refers to the ribonucleic acid rich fraction, sedimen- 

 ted in the ultracentrifuge when a cell-free homogenate is subjected to 

 differential centrifugation under certain standard conditions [14, i, 10]. 

 This definition does not involve any particular implications as to the cyto- 

 logical homogeneity of this fraction which consists of ribonucleoprotein 

 particles and different types of endoplasmic membranes. It may contain a 

 good number of subcellular elements which are functionally unrelated and 

 of different origin [13]. The enzymic or electron microscopic criteria 

 applied for the characterization of the microsomal fractions in this type of 

 work are the same as those available in other biochemical studies, e.g. 

 [i4> 28, 7]. 



Antigens in microsomes of liver and other organs of the rat 



So far, rat livers have constituted the most thoroughly studied material. 

 The analytical reagents are antisera obtained from rabbits injected either 

 with total microsomes or with microsomal subfractions, with the final 

 supernatant after removal of the microsomes ("cell sap"), or with rat 

 serum proteins. Details may be found elsewhere [i, 10]. When such 

 antisera are reacted on agar diffusion plates according to Ouchterlony [12] 

 one obtains complicated patterns of antigen-antibody precipitates. Most of 



* Parts of this work were carried out during a tenure of a Special Research 

 Fellowship granted by the National Cancer Institute, U.S. Public Health Service. 

 — Permanent address : Department of Pathology, Massachusetts General Hospital, 

 Boston, 14, Mass., U.S.A. 



