EFFECT OF O-2 EXPOSURE ON PULMONARY METABOLISM OF PROSTAGLANDIN-E2

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Abstract
The effect of exposure to O2 on lung metabolism of prostaglandin [PG]E2 to 15-keto-PGE2 and 13-14-dihydro-15-keto-PGE2 was studied in the isolated, perfused rat lung. During a 30 s period, lungs were infused with varying concentrations of PGE2 labeled with 3H and the fraction metabolized during 1 passage was determined. At a PGE2 concentration of 5 nM, which approximates that in normal mixed venous blood, an average of 93% of infused PG was metabolized by normal lungs. At PGE2 concentrations of 2-70 .mu.M, the fraction metabolized decreased. The computed concentration of PGE2 for half-maximal rate of metabolism was 4.2 .mu.M. Metabolism of PGE2 by isolated lungs was unaffected by exposure of rats to > 97% O2 at 1 atm absolute for 24 h, but was markedly depressed after both 36 and 48 h of hyperoxia. Exposure of the rat to O2 for 36 and 48 h is associated with decreased ability of the lung to metabolize PGE2 to its keto derivatives and may result in increased concentration of PGE2 in the systemic arterial blood.