| Abstract: | Balb/3T3 cells transformed in culture by chemical carcinogens were shown to multiply in a medium supplemented with 2% calf serum or with 10% agamma new-born calf serum. The cell lines that multiply well in medium supplemented with 10% agamma serum produced a higher incidence of tumors in X-irradiated weanling mice than the lines that multiply poorly. The difference in 2-deoxy-D-glucose uptake into exponentially growing transformed and un-transformed cells was 50–100%. In crowded cultures untransformed Balb/3T3 cells ceased taking up the sugar, while chemically transformed cells continued at the same rate even at high cell densities; thus, the difference became greater in crowded cultures. When the serum concentration in the media was reduced from 10% to 2%, untransformed Balb/3T3 cells took up the sugar at a reduced rate, while chemically transformed cells were only slightly affected; agamma new born calf serum supplemented medium had no effect on sugar uptake in any of the cells. When the serum concentration was changed from 2% to 10%, untransformed cells increased sugar uptake followed by cell division. The immediacy (within 15 min) of the response in the sugar uptake to 10% serum concentration suggested that the increased uptake rate and the consequent higher concentration of the sugar (D-glucose in normal situation) within Balb/3T3 cells triggered the cell cycle. Chemical carcinogens appear to alter permanently the uptake mechanism for a key nutrient. |
