Evidence that cytosolic and ecto 5 '-nucleotidases contribute equally to increased interstitial adenosine concentration during porcine myocardial ischemia
Rd. Lasley et al., Evidence that cytosolic and ecto 5 '-nucleotidases contribute equally to increased interstitial adenosine concentration during porcine myocardial ischemia, BAS R CARD, 94(3), 1999, pp. 199-207
The purpose of this study was to determine the roles of cytosolic and ecto
5'-nucleotidase in myocardial ischemia-induced increases in interstitial fl
uid (ISF) adenosine. Pentobarbital anesthetized, open chest pigs were instr
umented with two microdialysis fibers in the distally perfused bed of the l
eft anterior descending (LAD) coronary artery to estimate ISF metabolites.
Fibers in control hearts were perfused with standard Krebs buffer. In two a
dditional groups, after collecting one dialysate sample with normal Krebs,
fibers were perfused with buffer supplemented with either L-homocysteine th
iolactone (5 mM) or the ecto 5'-nucleotidase inhibitor alpha, beta-methylen
e adenosine 5'-diphosphate (AOPCP, 5 mM). Hearts were then submitted to 60
minutes LAD occlusion and two hours reperfusion. Dialysate nucleosides and
AMP were measured by high performance liquid chromatography The local deliv
ery of homocysteine did not alter preischemic dialysate adenosine concentra
tion (0.30 +/- 0.04 mu M) compared to pre-homocysteine infusion (0.39 +/- 0
.04 mu M) or control hearts (0.36 +/- 0.04 mu M), but AOPCP significantly d
ecreased preischemic dialysate adenosine levels (from 0.36 +/- 0.02 to 0.14
+/- 0.03 mu M). During LAD occlusion both homocysteine and AOPCP reduced d
ialysate levels by approximately 50%. At 30 minutes ischemia dialysate aden
osine concentrations were 19.47 +/- 2.72, 11.41 +/- 2.44, and 7.93 +/- 1.01
mu M in control, homocysteine, and AOPCP hearts, respectively. AOPCP signi
ficantly increased dialysate AMP levels; at 60 minutes ischemia AMP levels
were 6.22 +/- 2.97 mu M in control hearts and 38.60 +/- 5.69 mu M in AOPCP
treated hearts. These results suggest that both cytosolic and ecto 5'-nucle
otidase contribute to ischemia-induced increases in ISF adenosine in porcin
e myocardium.