Dexamethasone effect on renal prostaglandin-9-ketoreductase activity in the rabbit

The effect of in vivo administration of dexamethasone (1 mg/kg/d for 1 wk) was investigated on the ratio of urinary PGE2/PGF2 alpha excretion and on in vitro cortical prostaglandin-9-ketoreductase (PG-9-KR) activity in rabbits. Dexamethasone treatment decreased PGF2 alpha excretion significantly from 32.87 +/- 8.09 to 19.28 +/- 6.14 ng/mg creatinine, p less than 0.05) without causing a significant change in PGE2 excretion (9.38 +/- 2.48 and 13.53 +/- 5.03 ng/mg creatinine before and after dexamethasone, respectively). The ratio of urinary PGE2/PGF2 alpha increased markedly following glucocorticoid administration (from 0.34 +/- 0.08 to 1.03 +/- 0.32, p less than 0.05). The activity of cytosolic PG-9-KR activity, however, was not significantly different in control and dexamethasone-treated rabbits. It is concluded that the glucocorticoid-induced increase in urinary PGE2/PGF2 alpha ratio is probably unrelated to changes in PG-9-KR activity.