Differential effects of catecholoestradiol-17 beta and oestradiol-17 beta on concentrations of plasma LH in the fetal pig

The effects of 2-hydroxyoestradiol-17 beta and oestradiol-17 beta on the concentration of serum LH was studied in fetal pigs. 2-Hydroxyoestradiol-17 beta (5 micrograms/fetus; n = 6), oestradiol-17 beta (5 micrograms/fetus; n = 7) or vehicle (n = 6) were injected i.v. into chronically catheterized fetal pigs at gestational ages of 105-108 days. Seven additional fetuses at the same age served as untreated controls. 2-Hydroxyoestradiol-17 beta but not oestradiol-17 beta resulted in a rapid decline in plasma LH levels from 0.82 +/- 0.21 (S.E.M.) to 0.21 +/- 0.05 micrograms/l within 20 min of injection. Baseline concentrations of plasma LH in the mothers were low (0.72 +/- 0.2 microgram/l) and were not affected by catecholoestrogen or oestrogen treatment of fetuses. The results suggest that catecholoestrogens do not modulate LH secretion in fetal pigs through an oestrogenic action. It is possible that they act by modifying catecholamine metabolism or neurotransmission.