Effects of prolactin on the luteinizing hormone response to gonadotropin- releasing hormone in primary pituitary cell cultures during the ovine annual reproductive cycle
| Autor: | Domingo J. Tortonese, Julie Townsend, Alan S. McNeilly, Susan J. Gregory |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
endocrine system
Pituitary gland medicine.medical_specialty Gonadotropin-releasing hormone Biology Gonadotropic cell Gonadotropin-Releasing Hormone Hormone Antagonists Internal medicine medicine Animals Bromocriptine Cells Cultured Sheep Reproduction Osmolar Concentration Cell Biology General Medicine Luteinizing Hormone Prolactin Gonadotropin secretion Rats medicine.anatomical_structure Endocrinology Reproductive Medicine Pituitary Gland Female Seasons Luteinizing hormone hormones hormone substitutes and hormone antagonists Endocrine gland medicine.drug |
| Zdroj: | Biology of reproduction. 70(5) |
| ISSN: | 0006-3363 |
| Popis: | In the sheep pituitary, the localization of prolactin (PRL) receptors in gonadotrophs and the existence of gonadotroph-lactotroph associations have provided morphological evidence for possible direct effects of PRL on gonadotropin secretion. Here, we investigated whether PRL can readily modify the LH response to GnRH throughout the ovine annual reproductive cycle. Cell populations were obtained from sheep pituitaries during the breeding season (BS) and the nonbreeding season (NBS), plated to monolayer cultures for 7 days, and assigned to receive one of the following treatments: 1) nil (control), 2) acute (90- min) bromocriptine (ABr), 3) chronic (7-day) bromocriptine (CBr), 4) ABr and PRL, 5) CBr and PRL, 6) PRL alone, or 7) thyrotropin-releasing hormone. Cells were treated as described above, with the aim of decreasing or increasing the concentrations of PRL in the culture, and simultaneously treated with GnRH for 90 min. The LH concentrations in the medium were then determined by RIA. GnRH stimulated LH in a dose-dependent manner during both stages of the annual reproductive cycle. During the NBS, single treatments did not significantly affect the LH response to GnRH. However, when PRL was combined with bromocriptine, either acutely or chronically, GnRH failed to stimulate LH release at all doses tested (P < 0.01). In contrast, during the BS, the LH response to GnRH was not affected by any of the experimental treatments. These results reveal no apparent effects of PRL alone, but an interaction between PRL and dopamine in the regulation of LH secretion within the pituitary gland, and a seasonal modulation of this mechanism. |
| Databáze: | OpenAIRE |
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