Bromination of guanosine and cyclic GMP confers resistance to metabolic processing by B cells.

The metabolic fates of 8-bromoguanosine (8BrGuo) and 8-bromoguanosine-3'5'-cyclic monophosphate (8Br-cGMP) were examined in cultures of murine B lymphocytes. These compounds exert striking immunostimulatory effects upon bone marrow-derived lymphoid cells in vitro. Both 8BrGuo and 8Br-cGMP were resistant to metabolic processing by these cells. That purine metabolic pathways are intact and operant in B cells was demonstrated by the ready degradation and phosphorylation of native guanosine and cyclic GMP. Inaccessibilty of the substrate to the relevant enzymes was ruled out as an explanation by the observation that the brominated compounds also were resistant to processing in broken cell preparations. Moreover, 8BrGuo did not interfere with the cellular machinery for metabolizing native guanosine. The implications of these observations for studying the actions of purine nucleotides, cyclic nucleotides, and their enzymatic processing in B cells are discussed.