Does caffeine inhibit cardiac AMP deaminase?

Caffeine was recently shown to drastically increase plasma adenosine in rats. We hypothesized that this effect is due to caffeine-induced inhibition of AMP deaminase. For two weeks rats had water with 0.1% caffeine (C++) or caffeine withdrawn 14 h prior to the experiments (C+-), or they received plain water (C-). Langendorff perfused hearts were subjected to 20 min no-flow ischemia and 30 min reperfusion. During normoxia, the levels of ATP, phosphocreatine (PCr) and inorganic phosphate (P-i) were higher in the C++ group (P<0.05 vs C+- and C-). The high-energy phosphates decreased severely during ischemia and Pi increased. Caffeine withdrawal apparently suppressed adenosine production due to ischemia. Our data are consistent with the hypothesis, supported by preliminary in vitro evidence, that caffeine does inhibit AMP deaminase.