Effect of saccharin on metabolic cooperation between human fibroblasts

Autoradiography was used to study the effect of saccharin on metabolic cooperation between human diploid fibroblasts. When the donors, HGPRT+ cells, and recipients, HGPRT- cells, were plated together in the presence of saccharin, all the interactions that developed in 4 and 24 h were positive for metabolic cooperation. When saccharin was added after donor cells and recipient cells had made contact, the proportion of interactions that were positive for metabolic cooperation was unchanged but the number of grains over primary recipients was reduced. However, in donor cells saccharin caused a reduction in [3H]hypoxanthine incorporation into both acid-soluble and acid-insoluble fractions, although the relative distribution of radioactivity between these two fractions and between the phosphorylated and non-phosphorylated derivatives of [3H]hypoxanthine was unchanged. Metabolic cooperation was studied under conditions in which the number of grains over the nuclei of both the primary recipient and the primary recipient's donor could be counted. The change in the number of grains over these two cell types in response to saccharin was compared and found to be the same. Thus in normal human fibroblasts saccharin does not appear to affect metabolic cooperation, which is a measure of cell-to-cell communication.