In vivo 31P-MR spectroscopy of the liver in the infant rabbit to study the effect of hypoxia on the phosphorus metabolites and intracellular pH.

In vivo 31P-magnetic resonance spectroscopy (MRS) with a chronically implanted detection coil was used to study the effect of hypoxia on the phosphorus metabolites and intracellular pH in the liver of infant rabbits. A two-turn 10-mm radiofrequency coil was placed between the hepatic lobes in each of four infant New Zealand white rabbits (10-16 days old). Two days later, the rabbits were anesthetized and mechanically ventilated with 1.5% isoflurane in 98.5% O2. Blood gases, heart rate, and mean arterial pressure were monitored. 31P-MR spectra were continuously obtained every 5 minutes during 15 minutes of hyperoxia (PaO2 greater than 250 torr), 15 minutes normoxia (PaO2 approximately equal to 100 torr), 60 minutes hypoxia (PaO2 = 24 torr +/- 4 S.D.), and 15 minutes recovery (hyperoxia). In addition, 31P-MR spectra of perchloric-acid extracts of the liver of an adult and of an infant rabbit, removed under normoxic conditions, were examined. The 31P-MR spectra of liver of the normoxic adult (in vitro) and infant rabbits (in vitro and in vivo) revealed a high level of phosphodiesters, namely glycerol-3-phosphorylethanolamine, glycerol-3-phosphorylcholine, and phosphoenolpyruvate, compared with that reported for adult rat and adult mouse liver. The inorganic phosphate (Pi)-to-adenosine triphosphate (ATP) ratio was about 0.90 during hyperoxia and during normoxia. Within 15 minutes after induction of hypoxia, the level of phosphorus metabolites changed markedly: The ATP decreased 41% +/- 18 S.D. (P less than .01) and the Pi increased 206% +/- 29 S.D. (P less than .01); the Pi/ATP ratio was 5.0.(ABSTRACT TRUNCATED AT 250 WORDS)