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  • 1
    ISSN: 1435-1803
    Keywords: Adenosine deaminase ; microdialysis ; micropig ; myocardial blood flow ; pentostatin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to examine the relationship between local adenosine concentrations before, during, and after ischemia and the extent of ischemic myocardial damage, measurements of interstitial fluid (ISF) nucleosides were made using microdialysis probes implanted in the ischemic region of isoflurane anesthetized Micropigs undergoing 60′ coronary artery occlusion (CAO) and 3h of reperfusion (REP). Nucleoside concentrations in the dialysate collected from the microdialysis probes were used as an index of ISF levels. Dialysate nucleoside concentrations (ADO, inosine and hypoxanthine), myocardial infarct size, and myocardial blood flow (MBF) were determined in control animals (n=6), animals preconditioned with a single 10′ cycle of CAO and REP (PC, n=6), and those treated with the adenosine deaminase inhibitor pentostatin (n=6, 0.2 mg/Kg IV 30′ prior to CAO). The brief PC occlusion resulted in a transient but significant increase in dialysate ADO (6.7±1.8 μM vs. 0.67±0.1 μM at baseline). Pentostatin administration had no significant effect on either dialysate nucleosides or MBF at baseline. During the 60′ CAO, dialystate ADO increased in control animals. In PC animals, however, dialysate ADO during CAO was lower than control. Pretreatment with pentostatin resulted in a six-fold augmentation in dialysate ADO during the 60 min CAO when compared to the control values (110.62±30.2 μM vs. 16.31±2.1 μM at 60 min of ischemia). Pentostatin also resulted in a significant reduction in the accumulation of inosine and hypoxanthine, indicating inhibition of adenosine deaminase activity. There were no significant differences in MBF between groups at any time point. Following 3 h REP, infarct size was 35.4±5.5%, 8.1±1.5% and 8.3±1.8% of the region at control, PC, and pentostatin groups, respectively. These data suggest that marked increase in ISF ADO during CAO, may be as effective in reducing INF as a modest increase in ISF ADO prior to prolonged CAO.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-1803
    Keywords: Adenosine deaminase ; adenosine ; myocardial stunning ; sonomicrometers ; microspheres ; dog
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Pentostatin (2-deoxycoformycin) is a potent inhibitor of adenosine deaminase and has been demonstrated to augment endogenous adenosine levels during regional and global myocardial ischemia. Based on the rationale that increasing endogenous adenosine during ischemia may be cardioprotective, the objective of this study was to determine if adenosine deaminase inhibition with pentostatin could improve postischemic contractile dysfunction (stunning) in open-chest anesthetized dogs. All animals underwent 15 min of coronary occlusion followed by 3 h of reperfusion preceded by an intravenous bolus of either 0.2 mg/kg of pentostatin (n=8) or saline (n=7). Sonomicrometers were plced in the ischemic area and were used to measure systolic wall thickening before, during, and after occlusion of the left anterior descending artery. Myocardial blood flow was measured with tracer labeled microspheres at baseline, 10 min of occlusion and at 1 h of reperfusion. Both groups were equally dyskinetic during occlusion (−21±5% of baseline thickening in the controls and −28±8% in the pentostatin group). The pentostatin group, however, demonstrated better contractile function at all time points during reperfusion, which was significantly different from the control group at 3 h of reperfusion. The improvement in regional function in the pentostatin group was not due to significant disparities in hemodynamic variables, size of the region at risk, or in collateral blood flow. These results indicate that pentostatin can ameliorate the severity of myocardial stunning, an effect we propose is due to increasing endogenous levels of adenosine during the ischemic interval. Although significant improvement was detected with pentostatin, the improvement was modest compared to controls, suggesting that the utility of inhibiting adenosine deaminase to modify regional mechanical stunning is limited.
    Type of Medium: Electronic Resource
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