Distribution of prostaglandin omega-hydroxylases in different tissues.

The conversion of prostaglandins E2 and F2 alpha to their 19- and 20-hydroxy metabolites by various tissues has been measured by gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring. A number of different tissues of the pregnant rabbit possess prostaglandin 20-hydroxylase activity (lung > liver > fetal placenta > maternal placenta approximately equal to uterus > renal cortex > renal medulla approximately equal to placental membranes). With the exception of the liver, prostaglandins E2 and F2 alpha are metabolized at equal rates by the 20-hydroxylases of different tissues. Only lung and liver microsomes posess high levels of prostaglandin 20-hydroxylase in non-pregnant rabbits and only liver microsomes have appreciable 19-hydroxylase activity. Pulmonary prostaglandin 20-hydroxylase is induced in male rabbits by treatment with progesterone. On the basis of substrate specificity studies and the effects of a cytochrome P-450 inhibitor, SKF-525A, the prostaglandin 20-hydroxylases of lung and liver microsomes from pregnant rabbits appear to be different enzymes. In pregnant rats and hamsters, liver and kidney are the only tissues in which we detected prostaglandin omega-hydroxylase activity.