Further serum related alterations in the activities of some membrane marker enzymes in normal and virus transformed cells

The activities of membrane marker enzymes in normal (3T3) and simian virus transformed mouse cells (SV3T3) are affected not only by densities of cultures but also by the sera types used in the growth media. We have assayed the levels of 5'nucleotidase, monoamine oxidase and rotenone insensitive NADH ferricyanide reductase in these cells grown to sparse and confluent cultures in medium supplemented with 10% newborn calf serum (n.c.s.) or in medium supplemented with 10% foetal bovine serum (f.b.s.). It was found that in 3T3 cells grown in 10% f.b.s. the transition from sparse to confluent cultures was associated with a reduction in the activities of the marker enzymes while in those grown in 10% n.c.s., the activities of these enzymes increased. In the SV3T3 cells, the activities of all the enzymes except for monoamine oxidase decreased from sparse to confluent culture densities in cells grown in 10% n.c.s. whereas in those grown in 10% f.b.s. there were no significant change in the activities of the enzymes over the same culture densities. The results suggest that the marker enzymes are affected by sera types and culture densities.