Oxygen consumption of the kidney has been found to be much higher than that of the liver. The present study was performed to clarify its biological significance related to its function, through the metabolic pattern of the nucleotides of the kidney, comparing with that of the liver. Male rats weighing 100-150 g, after administered iP
32 (100μc/100 g) intraperitoneally, were decapitated and kidney and liver tissues were removed and immediately frozen. Oxygen consumption of both organs was determined by the Warburg's method. Acid soluble nucleotides were extracted with PCA from the frozen tissues and chromatographed through ion exchange resin column with formic system, then rechromatographed with formate system. Charcoal column chromatography or isobutanol extraction was applied for further purification of fraction of sugar phosphate or iP, respectively. Results obtained were as follows: 1) Kidney showed a much higher value in tissue respiration than that of liver. 2) Amount of total acid soluble nucleotides of the kidney was less than that of the liver. 3) Ratio of adenosine nucleotides to total nucleotides was 61.3% in the kidney and 60.5% in the liver, if respiratory cofactors (DPN, TPN, Ad-X) were excluded. That of uridine nucleotides was. w 30.7% in the former, while 35.5% in the latter, and that of guanosine nucleot ides 6.5% in the former, while 3.6% in the latter. 4) Kidney had more DPN than liver in its amount. 5) ATP/ADP ratio and ADP/AMP ratio were markedly lower in the kidney. On the contrary, UTP/total uridine nucleotides ratio was higher in kidney, and GTP/GDP ratio was almost the same between both organs. 6) The value of RSA(ATP) calculated by the incorporation of iP
32 was much lower in the kidney (0.62/16 min., 1.04/25 min.) than in the liver (1.56/10 min., 1.78/15 mm.). 7) No retardation was found in the turnover between ADP and ATP even in the kidney accordingto SA(ADP)/SA(ATP). The ratio reached a higher value at 25 min, than that of the theoreticall equilibrium (2/3), while such a tendency could not be seen in the liver. 8) SA (nucleoside triphosphate)/SA(ATP) and SA(nucleoside diphosphate)/SA(ADP) ratio was close to 1 with uridine nucleotides and guanosine nucleotides in the kidney as well as in the liver. 9) The amount of hexose monophosphate was almost the same in both organs. In the kidney, the phosphte of hexose monophosphate and terminal phosphate of ATP were observed to be isotopically equilibrated in 25 min. When compared with the liver, the kidney could be characterized by its higher activity in tissue respiration associated with a low ATP/ADP ratio, as well as by markedly slow iP-ATP exchange (RSA(ATP)), representing an activity of oxidative phosphorylation in vivo. From these results and above-mentioned nucleotides pattern it seems possible that the kidney utilizess directly much more 'high energy intermediate of oxidative phosphorylation' other than ATP, probably as the source of energy in osmotic and transport work. In addition, a high activity of myokinase, and ATPase can be expected from above mentioned nucleotides pattern, and relatively slow ADP-ATP exchange observed will support such an assumption.
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