The functional changes of cytoplasmic membrane of mammalian cells as a
n alternative approach for evaluating the tumor promoter activity were
investigated. The V79 metabolic cooperation assay, as the standard me
thod for detection of tumor promoters in vitro was used, From three kn
own tumor promoters only phenobarbital increased the efflux of [H-3]2-
deoxy-D-glucose-6-phosphate from the cells in the same concentration r
ange where the inhibition of metabolic cooperation was estimated. Neit
her TPA, saccharin nor theophylline caused any functional changes of c
ytoplasmic membrane of V79 cells. On the basis of the results with kno
wn tumor promoters we suggest that following the functional changes of
cytoplasmic membrane is not a convenient approach for screening poten
tial tumor promoters.