A Comparison of Nuclear to Microsomal Amino-acid Incorporation into Developing and Lactating Mammary Tissue

Abstract

IN the investigation of amino-acid incorporation in vivo in various tissues, both neoplastic and normal, Campbell et al.¹ and Busch et al.² have reported that in neoplastic tissues the nuclear fraction exhibits a higher rate of incorporation, relative to that of the microsomal fraction, than is the case in normal tissue. They postulated with some reservation that this elevated nuclear incorporating activity is a phenomenon associated with the neoplastic state. However, they did not examine the pattern of relative incorporations in any rapidly dividing normal tissues, and it is possible that such an incorporation pattern may be more a characteristic of rapid cell division than of neoplasia per se. Therefore, it would be pertinent to compare a normal tissue, preferably one the protein synthesis of which is directed toward secretory products, to a tissue which is rapidly growing, one the protein synthesis of which is directed toward mitosis and the production of structural elements.