The present study was conducted to determine the metabolism of renal interstitial
adenosine under resting conditions and during
ischemia. By using a microdialysis method with HPLC-fluorometric analysis, renal interstitial concentrations of
adenosine,
inosine, and
hypoxanthine were assessed in
pentobarbital-anesthetized dogs. Average basal renal interstitial concentrations of
adenosine,
inosine, and
hypoxanthine were 0.18 +/- 0.04, 0.31 +/- 0.05, and 0.35 +/- 0.05 micromol/l, respectively. Local inhibition of
adenosine kinase with iodotubercidin (10 micromol/l in perfusate) or inhibition of
adenosine deaminase with erythro-9-(2-hydroxy-3-nonyl)adenine (
EHNA; 100 micromol/l in perfusate) did not change
adenosine concentrations in the nonischemic kidneys (0.18 +/- 0.04 and 0.24 +/- 0.05 micromol/l, respectively). On the other hand, treatment with iodotubercidin+EHNA significantly increased
adenosine concentration (0.52 +/- 0.07 micromol/l) with significant decreases in
inosine and
hypoxanthine levels (0.13 +/- 0.03 and 0.19 +/- 0.04 micromol/l, respectively). During 30 min of
ischemia,
adenosine,
inosine, and
hypoxanthine were significantly increased to 0.76 +/- 0.29, 2.14 +/- 0.45, and 21.8 +/- 4.7 micromol/l, respectively. The treatment with iodotubercidin did not alter
ischemia-induced increase in
adenosine (0.84 +/- 0.18 micromol/l); however,
EHNA alone markedly enhanced
adenosine accumulation (13.54 +/- 2.16 micromol/l), the value of which was not augmented by an addition of iodotubercidin (15.80 +/- 1.24 micromol/l). In contrast,
ischemia-induced increases in
inosine and
hypoxanthine were inversely diminished by the treatment with iodotubercidin+EHNA (0.90 +/- 0.20 and 9.86 +/- 1.96 micromol/l, respectively). These results suggest that both
adenosine kinase and
adenosine deaminase contribute to the metabolism of renal interstitial
adenosine under resting conditions, whereas
adenosine produced during
ischemia is mainly metabolized by
adenosine deaminase and the rephosphorylation of
adenosine by
adenosine kinase is small.sent