[Correlation between the proliferative activity and protein kinase C activities in ethidium bromide-sensitive and -resistant cells].

The protein kinase C (PK C) activity was determined in the cytosolic and membrane fractions of L- and CHO-K1-cells, both sensitive and resistant to ethidium bromide (EB). In the resistant cells (Lebr-25 and Cebr) a decreased enzyme activity was found in addition to alteration of the enzyme elution profile in the membrane preparations purified by DE-52 cellulose column chromatography. Methyltestosterone treated cells had a decreased enzyme activity in nonpurified membrane preparations in Lebr-25 cells, whereas the enzyme quantity in purified preparations remained the same. The decreased PK C activity on membranes correlates with the rapid proliferation of the resistant cells. The differences found between Lebr-25 and Cebr-cell lines in proliferation response to methyltestosterone correspond to the change of PK C developed due to hormone treatment.