Augmentation of Pituitary Responsiveness to Luteinizing Hormone/Follicle Stimulating Hormone-Releasing Factor (LH-RF) as a Result of Acute Ovariectomy i n the Four-day Cyclic Rat
| Autor: | C. P. Fawcett, K. J. Cooper, Samuel M. McCann |
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| Rok vydání: | 1975 |
| Předmět: |
endocrine system
medicine.medical_specialty Pituitary gland Time Factors In Vitro Techniques Gonadotropin-Releasing Hormone Endocrinology Estrus Pregnancy In vivo Internal medicine medicine Animals Follicle stimulating hormone releasing factor Castration Incubation reproductive and urinary physiology Estrous cycle urogenital system Chemistry Ovary Diestrus Luteinizing Hormone In vitro Rats medicine.anatomical_structure Pituitary Gland Female Proestrus Follicle Stimulating Hormone Luteinizing hormone hormones hormone substitutes and hormone antagonists |
| Zdroj: | Endocrinology. 96:1123-1129 |
| ISSN: | 1945-7170 0013-7227 |
| DOI: | 10.1210/endo-96-5-1123 |
| Popis: | Within 6 h of ovariectomy in adult rats with 4-day estrous cycles, plasma FSH titers were significantly elevated above those of sham-operated controls at all stages of the estrous cycle, whereas plasma LH concentrations were raised by ovariectomy only during diestrus day 2, proestrus or estrus. A single intravenous injection of a partially purified extract of ovine stalk-median eminence tissue (LH-RF) into sham-operated control rats or incubation of pituitaries from similar rats with the same releasing factor extract elevated LH and FSH output at all stages of the cycle. This response to LH-RF was related to the stage of the estrous cycle, maximal pituitary responsiveness occurring on proestrus. Ovariectomy 6 h before administration of LH-RF significantly augmented pituitary LH and FSH responsiveness both in vivo and in vitro. This elevation in hypophyseal responsiveness observed in vitro followed a cyclic pattern which could be superimposed on the normal cyclic changes in pituitary responsiveness, whereas the cyclic increase in pituitary LH responsiveness to LH-RF in vivo following acute ovariectomy was first detectable 16 to 18 h earlier than in intact controls, that is, on late diestrus day 2 rather than on the morning of proestrus. These results indicate that acute ovariectomy can augment pituitary responsiveness to LH-RF and can also advance the onset of the cyclic augmentation of pituitary responsiveness to LH-RF during the 24 h immediately preceding the ovulatory gonadotropin surge. Possible explanations for these effects are discussed. |
| Databáze: | OpenAIRE |
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