Compartmentalized ATP pools produced from adenosine are nuclear pools

Abstract

Incubation of African green monkey kidney (BS‐C‐1) cells and mouse fibroblasts (3T6) in the presence of adenosine for 4 hours resulted in increases in the nuclear compartment pools of adenosine 5′‐triphosphate (ATP) and nuclear ATP/adenosine 5′‐diphosphate (ADP) ratios. Adenine and inosine, which yield increases in total cellular ATP pools and ATP/ADP ratios similar to those promoted by adenosine, do not produce similar increases in the nuclear compartment. Adenosine‐promoted increases in nuclear ATP pools were higher in the untransformed, serially propagated, BS‐C‐1 cells than in the spontaneously transformed 3T6 cells. Adenosine‐promoted compartmentalized ATP pools in primary chick embryo fibroblasts were reduced upon transformation of these cells with Rous sarcoma virus, resulting in free mixing of all the ATP pools synthesized from various salvage precursors. The growth regulatory properties of the nuclear compartment pools of adenine nucleotides is suggested by the big increases in nuclear ATPase and adenosine 5′‐monophosphate (AMP) demainase activities upon the entry of 3T6 cells into the S phase of their cycle. These enzymatic activities would tend to lower the nuclear ATP/ADP ratios and reduce the total adenine nucleotide pools in these nuclei respectively – conditions which were shown by earlier in vitro studies to be favorable to DNA replication.