STUDIES ON PLASMA MEMBRANES .X. A SURVEY OF ENZYME ACTIVITIES DISPLAYED BY PLASMA MEMBRANES ISOLATED FROM MOUSE LIVER AND 3 MOUSE HEPATOMA STRAINS

Plasma membranes were isolated from CBA‐mouse liver and three transplanted mouse hepatomas having spontaneously arisen in old CBA males. The membranes were assayed for enzymes which had previously been demonstrated in isolated rat‐liver plasma membranes. Marked differences in the specific activities of some enzymes (e.g. 5′‐mononucleotidase) of mouse‐ and rat‐liver membranes were noted. The changes observed in the specific enzyme activities and the stability of certain enzymes of the hepatoma membranes, relative to the corresponding properties of liver membranes, were of three types: (a) those common to all three hepatomas; (b) changes restricted to individual hepatoma strains; and (c) changes developing during the natural history of a given hepatoma strain maintained by transplantation. It is concluded that tumor individuality and progression are expressed at the level of the plasma membrane enzymes. The number of changes in plasma membrane enzymes of a particular hepatoma relative to liver may serve as a measure of deviation of that tumor from the homologous normal resting tissue, but the impact of these membrane changes on tumor‐cell behavior is unknown. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company