Estradiol is responsible for reduced renal prostaglandin dehydrogenase activity in female rats

The contribution of sex steroids to sex-related differences in renal prostaglandin dehydrogenase activity and urinary prostaglandin excretion was examined in 7-8-week-old male and female rats subjected to sham-operation or gonadectomy at 3 weeks of age. Rats were injected subcutaneously twice over a 6-day interval with vehicle (peanut oil, 0.5 mg/kg) or with depot forms of testosterone (10 mg/kg), estradiol (0.1 mg/kg), progesterone (5 mg/kg), or with estradiol and progesterone combined (0.1 and 5 mg/kg). After the second injection, 24-h urine samples were collected for prostaglandin measurement by radioimmunoassay; the rats were killed, and renal and pulmonary prostaglandin dehydrogenase activities were determined by radiochemical assay. Renal prostaglandin dehydrogenase activity was 10-times higher in intact male rats than in intact females. Gonadectomy increased renal prostaglandin dehydrogenase activity 4-fold in females, but had no effect in males; estradiol, alone or combined with progesterone, markedly suppressed renal prostaglandin dehydrogenase activity in both sexes, while testosterone or progesterone alone had no effect. Pulmonary prostaglandin dehydrogenase did not differ between the sexes and was unaffected by gonadectomy or sex-steroid treatment. Intact female sham-operated rats excreted 70-100% more prostaglandin E2, prostaglandin F2 alpha, and 6-keto-prostaglandin F1 alpha in urine than did males; gonadectomy abolished the difference in urinary prostaglandin E2 excretion. Estradiol decreased urinary prostaglandin E2 in females but not in males; treatment with other sex steroids did not alter urinary prostaglandin excretion.