Effects of Catecholoestrogen-Benzoates on Gonadotrophin Secretion in Immature Female Rats

Summary

Immature female rats were injected on day 25 12:00 h with vehicle or different doses of oestradiol-benzoate (E₂ B; 1, 3, 10 μg) or 4-hydroxyoestradiol 3,4-dibenzoate (4-OHE₂ B₂; 1, 3, 10 μg) or 2-hydroxyoestradiol 2,3-dibenzoate (2-OHE₂ B₂; 10, 125 μg). On the evening of day 27 (18:00 h; 54 h after injection) LH- and FSH-responses were studied: E₂ B induced a significant elevation of LH- and FSH-surge frequencies in all doses tested. 4-OHE₂ B₂ was effective at doses of 3 and 10 μg with a tendency of more pronounced responses than those obtained with equal doses of E₂ B. 2-OHE₂ B₂ was not effective at the 10 μg dose but induced a significant gonadotrophin response at a dose of 125 μg.

In a second experiment the effects of ovulatory doses (25 μg) of E₂ B of 4-OHE₂ B₂ were studied on the evenings of days 26, 27, 28 and 29. Animals treated with 4-OHE₂ B₂ had a significant elevation of the LH- and FSH-surge frequencies on day 27 (54 h after injection), whereas the gonadotrophin responses were low on all other days. E₂ B induced a significant rise of the LH- and FSH-surge frequencies on day 28 (78 h after injection). On days 26, 27 and 29 the gonadotrophin responses in E₂ B-treated animals were higher than in the control groups. 2-OHE₂ B₂ (125 μg) tested in the same way induced a pattern of LH- and FSH-secretion which was similar to that of 4-OHE₂ B₂ (25 μg). These findings might indicate that catecholoestrogens and primary oestrogens have qualitatively different effects on the gonadotrophin secretion in immature female rats.

Key-Words:

Catecholoestrogens - Gonadotrophins - Immature Rat