Oestradiol-17beta and pituitary responsiveness to luteinizing hormone releasing factor in the rat: a study using rectangular pulses of oestradiol-17beta monitored by non-chromatographic radioimmunoassay
| Autor: | S. R. Henderson, Christine Baker, George Fink |
|---|---|
| Rok vydání: | 1977 |
| Předmět: |
endocrine system
medicine.medical_specialty Time Factors Endocrinology Diabetes and Metabolism Sodium chemistry.chemical_element Endogeny Capsules Gonadotropin-Releasing Hormone Endocrinology Estrus Pregnancy Internal medicine medicine Animals Castration Pentobarbital Estrous cycle Estradiol Chemistry Uterus Radioimmunoassay Silastic Luteinizing Hormone Rats Pituitary Gland Ovariectomized rat Oestradiol 17β Female Luteinizing hormone releasing factor Follicle Stimulating Hormone hormones hormone substitutes and hormone antagonists |
| Zdroj: | The Journal of endocrinology. 73(3) |
| ISSN: | 0022-0795 |
| Popis: | SUMMARY Plasma concentrations of oestradiol-17β were measured by a non-chromatographic radioimmunoassay during the oestrous cycle, after the s.c. injection of 2·5 or 10 pg oestradiol benzoate (OB), or the s.c. implantation of Silastic capsules containing crystalline oestradiol-17β. The profile of endogenous plasma oestradiol-17β concentrations was similar to that reported by other workers, and lay between the concentrations produced by the low and high doses of OB. The rectangular pulses of increased plasma oestradiol concentrations, produced during the period of implantation of the Silastic capsules, were used to determine the time taken for oestradiol-17β to exert its facilitatory effect on the gonadotrophin response to LH-releasing factor (RF). In animals ovariectomized at dioestrus, oestradiol, at concentrations similar to those reached during the peak of the spontaneous surge, first reduced the LH response. However, after 7 h, responsiveness increased significantly to reach a peak at 12 h. The FSH response was also greatest 12 h after ovariectomy. In animals ovariectomized at metoestrus the effect of oestradiol on the LH response was significantly less than in rats ovariectomized at dioestrus, and the FSH responses were lower than those in animals bearing empty capsules and examined at the same time after ovariectomy. These findings together with the effects of long-term exposure to sodium pentobarbitone are considered with respect to the possible mechanisms, including the priming effect of LH-RF, which may produce increased pituitary responsiveness after ovariectomy and exposure to oestrogen. |
| Databáze: | OpenAIRE |
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