Pyridine nucleotides in lung and liver of hypoxic rats

Abstract Adult male albino rats of Wistar strain in the weight range of 170–200 g were exposed to acute hypobaric hypoxia of 25,000 ft at 32°C for 90, 180, 270 and 360 min. respectively. The extramitochondrial dehydrogenases generating NADPH and the mitochondrial dehydrogenases generating NADH were studied in lung and liver. The oxidized and the reduced forms of these two nucleotides were determined at 90 min. and 360 min. of hypoxia. Hypoxia caused an initial decline in the activities of all the dehydrogenases studied. The activities of mitochondrial and pentose phosphate dehydrogenases of liver were high at 360 min. of hypoxia whereas the activities of extramitochondrial dehydrogenases of lung were generally low at all levels of hypoxic exposure. The NADPH levels of hypoxic rat lung were correspondingly low. However, the activities of liver mitochondrial dehydrogenases were elevated at 360 min. of hypoxia in spite of NADH accumulation in hypoxic rat liver. A decreased NAD/NADH ratio was observed in lung at 90 min. and 360 min. of hypoxia.