Purine salvage pathways for the biosynthesis in vitro of adenine nucleotides in the guinea pig vas deferens

The guinea pig vas deferens has been found to possess at least two active anabolic pathways for adenine nucleotide biosynthesis. Our studies in vitro show that ³H]adenosine and ³H]adenine may be important precursors in purine salvage. Both precursors are eventually converted to ³H]AMP prior to final incorporation into ³H]ATP. ³H]adenosine is transported across the cell membrane and then phosphorylated intracellularly to ³H]AMP with the subsequent formation of ³H]ADP and ³H]ATP. ³H]adenine, on the other hand, is probably converted to ³H]AMP by a mechanism that does not involve ³H]adenosine transport, since 6-nitrobenzylthioguanosine (6-NBTG), a nucleoside transport inhibitor, does not inhibit ³H]adenine utilization. Conversion of ³H]adenosine to ³H]inosine or ³H]hypoxanthine prior to incorporation into ³H]ATP is probably only of minor importance since: (1) 6-NBTG reduces ³H]adenosine conversion to phosphorylated adenine compounds by 90 per cent; and (2) the adenosine deaminase inhibitor, 6-thioguanosine, even at high concentrations could only slightly reduce the amount of ³H]ATP formed from ³H]adenosine. Incubation of vas deferens with either ³H]inosine or ³H]hypoxanthine also failed to result in appreciable labeling of adenine nucleotide pools. The relative contributions of tritium labeled nucleosides and bases to ³H]ATP synthesis in vitro in the guinea pig vas deferens are; ³H]adenosine > ³H]adenine ? ³H]inosine > ³H]hypoxanthme.