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
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Gonadotrophins
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Immature Rat
