Time-dependent loss of adenosine 5'-monophosphate deaminase activity may explain elevated adenosine 5'-triphosphate levels in senescent erythrocytes.

Senescent erythrocytes from rabbits were previously shown to have elevated levels of adenine nucleotides. The present study documents that aged red blood cells have a normal synthetic capacity for adenine nucleotides, as indicated by normal levels of adenosine kinase. However, senescent erythrocytes do have decreased levels of adenosine 5'-monophosphate deaminase, the critical enzyme involved in degrading adenine nucleotides. These circumstances of a normal synthetic capacity in the presence of decreased catabolic ability were observed previously in a human genetic deficiency of adenosine 5'-monophosphate deaminase; the red blood cells in these patients accumulate adenosine 5'-triphosphate as do senescent erythrocytes in rabbits.