Figure 5. Extracellular accumulation of released adenine nucleotides is controlled by the activities of both ecto-5′-nucleotidase and ecto-AMP deaminase.

AMP was quantified by HPLC in bath samples collected after 2.5 min incubation with the preparations during rest (basal) or after electrical stimulation (total) of the phrenic nerve trunk with 5 Hz trains. The ecto-5′-nucleotidase inhibitor, α,β-methylene ADP (AOPCP, 200 μm), and/or the ecto-AMP deaminase inhibitor, deoxycoformycin (dCOF, 200 μm), were added to the incubation medium 15 min before sampling. The absence (-) or presence (+) of each drug is indicated below each bar. T he evoked release of adenine nucleotides (evoked) was calculated by subtracting the basal release from the total release of adenine nucleotides. The data are means ±s.e.m. of 3–8 experiments. *P < 0.05 when compared with 0 nmol (mg tissue)⁻¹; **P < 0.05 when compared with the effect of either AOPCP or dCOF alone; ***P < 0.05 between the indicated bars.