Shifts in Gonadotropin and Steroid Levels That Precede Anestrus in Female Golden Hamsters Exposed to a Short Photoperiod 1
| Autor: | Kay L. Jorgenson, Neena B. Schwartz |
|---|---|
| Rok vydání: | 1985 |
| Předmět: |
Estrous cycle
endocrine system medicine.medical_specialty medicine.drug_class Cell Biology General Medicine Biology Endocrinology Reproductive Medicine Estrogen Internal medicine Follicular phase medicine Circadian rhythm Gonadotropin Luteinizing hormone hormones hormone substitutes and hormone antagonists Morning Hormone |
| Zdroj: | Biology of Reproduction. 32:611-618 |
| ISSN: | 1529-7268 0006-3363 |
| DOI: | 10.1095/biolreprod32.3.611 |
| Popis: | Female golden hamsters exposed to short photoperiods become anestrous and exhibit daily surges of gonadotropins and progesterone. Since little is known about the transition between the cycling and anovulatory states, the following experiments were done to determine whether there are hormonal changes that precede cessation of estrous cyclicity. Females killed on the morning of estrus, up to the tenth estrous cycle in short days, showed no hormonal or ovarian morphologic evidence of changes in reproductive function. When assessed on the afternoon of estrus, however, serum levels of luteinizing hormone and progesterone increased significantly before vaginal and ovarian cyclicity ceased. Females sampled in both the morning and afternoon at increasing durations since their last vaginal estrus revealed that maximal daily surges of both gonadotropins and progesterone were not consistently manifested until the vaginal cycle had been absent for 2 weeks. By then, estrogen levels and uterine weights were low and ovaries showed hypertrophied interstitia and arrested follicular growth. We have demonstrated that there are hormonal changes in females before the loss of the vaginal cycle and onset of major daily hormonal surges. Our results suggest that alterations in feedback relationships between steroid hormones and gonadotropins may precede photoperiod-induced anestrus. |
| Databáze: | OpenAIRE |
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