Time course of extracellular dGMP degradation catalyzed by enzymes.

Extracellular dGMP degradation was catalyzed by cell membrane-bound enzymes (A) or serum enzymes (B). The cells were incubated in RPMI 1640 medium supplemented with 10% or 20% FBS and containing 200 μM dGMP. Subsamples of extracellular medium to be used for HPLC analysis were taken at incubation times of 0, 24, 48, 72, and 96 hours and assayed for dGMP and deoxyguanosine. The concentrations were estimated from the peak areas obtained after HPLC. Data points in panel A represent means ± SDs from at least 3 experiments. (B) 2 indicates time course of dGMP degradation in RPMI medium supplemented with 20% heat-inactivated FBS. 1 and 3 indicate dGMP degradation in the medium taken from HeLa and HUVEC cultures, respectively, after their 72-hour incubation.