Kinetics of prostaglandin E metabolism in isolated hepatocytes

The kinetics of prostaglandin E metabolism were investigated in isolated hepatocytes from male Sprague-Dawley rats. [3H]Prostaglandin E1 or [3H]prostaglandin E2 was incubated with cells in suspension, aliquots were collected over time and samples extracted and chromatographed using reverse-phase high-performance liquid chromatography. Both prostaglandins E1 and E2 were rapidly metabolized by the hepatocytes and at low prostaglandin E concentrations (10(-12) M) both have similar apparent half-lives (prostaglandin E1, 1.24; prostaglandin E2, 1.68 min). Disappearance of counts from prostaglandin E1 and E2 fractions was accompanied by the appearance of counts in earlier fractions of the chromatograms, consistent with metabolism to compounds which are more polar than the native prostaglandins. The half-life for prostaglandin E1 was unchanged over a prostaglandin E1 concentration range of 10(-12) to 10(-6) M. In contrast, increasing prostaglandin E2 concentration resulted in a prolonged half-life over the same concentration range. Decreasing cell concentrations from 5 X 10(6) to 5 X 10(5) cells/ml resulted in decreases in the rates of metabolism of both prostaglandins E1 and E2.