INvestigation of the basis of reduced metabolic cooperation in mec- cells.

The basis for the apparent loss of metabolic co-operation in a line of mec^? cells derived by selection from a mec⁺ line has been investigated. The results indicate that the loss of pyrimidine deoxyribonucleotide co-operation in these cells is due neither to the dilution of transferred nucleotides by enlarged endogenous pools nor to the failure of distinct internal pools to equilibrate, but rather to a deficiency of intercellular junctions. This deficiency can be reversed by treatment of the cells with db-cAMP and theophylline which results in the restoration of co-operation for TdR nucleotides. The results also indicate that the residual junctional sites in mec^? cells can transfer TdR nucleotides under conditions where the mec⁺ donor pools are expanded.