Catabolism of purine mononucleotides to hypoxanthine and xanthine in the liver is enhanced in rats resuscitated after a 6.5-min asphyxia. Reduced incorporation of 14C-hypoxanthine into these nucleotides 30 min, 1, and 3 days after resuscitation attests to its disturbed reutilization. This probably promotes activation of the xanthine oxidase reaction, leading to purine deficit and hyperproduction of reactive oxygen species. Key Words: hypoxanthine; postresuscitation disturbancesAccumulation of hypoxanthine (HX) in tissues during the postresuscitation period results from enhanced catabolism of purine mononucleotides [3,4]. Activation of xanthine oxidase reaction renders this process irreversible [9]. Moreover, it has been previously hypothesized that in vivo activation of xanthine oxidase reaction leads to hyperproduction of reactive oxygen species [3,4,6]. An alternative pathway is reutilization of HX. Apart from hepatogenic HX, the liver metabolizes HX delivered by the blood [141, therefore disturbances in HX metabolism can have grave consequence for the whole organism. In the present study we evaluated the efficiency of HX reutilization in the liver of resuscitated rats. MATERIALS AND METHODSExperiments were carried out on 140 male rats weighing about 200 g. They were resuscitated after 6.5-min asphyxia as described previously [8]. They were narcotized with ether 30 and 90 min, 6 and 24 h, and 3, 7, and 21 days after resuscitation, a and the liver was ex vivo fixed in liquid nitrogen. Control rats were subjected to the same procedures except for asphyxia and resuscitation. 14C-HX was injected intravenously in a dose of 740 kBq/kg body weight 25Central Research Laboratory, State Medical Academy, Omsk min prior to f~ation. The liver was processed as described elsewhere [51.It is known that HX is converted not into inosine, but into inosine monophosphate and then into other nucleoside-monophosphates (NMP): adenylosuccinate, adenosine monophosphate, xanthosine monophosphate, guanosine monophosphate [9]. NMP are then phosphorylated to nucleoside di-and triphosphates (NDTP). Hence, reutilization 14C-HX can be assessed only by measuring radioactivity not only of major mononucleotides (ATP and GTP) but also of all purine mononucleotides; NDTP and NMP should be measured as two independent pools. The content of HX and xanthine in the liver was measured as described elsewhere [13], and label incorporation into purine NMP and NDTP and their content were determined by our methods. The data were processed statistically using the Student and Wilcoxon--Mann--Whitney tests and Spearman correlation coefficient [2]. RESULTSCatabolism of NMP and NDTP in the liver of resuscitated rats is enhanced, as evidenced by reduced content of these nucleotides and accmnulation of HX and xanthine (Table 1). Hypoxanthine is a common catabolite of all purine mononucleotides [11,12]. It can be hypothesized that HX formed during asphyxia

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