Gonadotropin-releasing hormone stimulates prolactin release from lactotrophs in photoperiodic species through a gonadotropin-independent mechanism
| Autor: | Domingo J. Tortonese, Helen L. Henderson, Julie Townsend, David J. Hodson, Susan J. Gregory |
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| Rok vydání: | 2007 |
| Předmět: |
endocrine system
Pituitary gland medicine.medical_specialty Periodicity medicine.drug_class Lactotrophs Receptors Prolactin Gene Expression Gonadotropin-releasing hormone Biology Breeding Gonadotropic cell Prolactin cell Gonadotropin-Releasing Hormone Receptors Gonadotropin Internal medicine Paracrine Communication medicine Animals Horses Cells Cultured Sheep Cell Biology General Medicine Receptors LH Prolactin medicine.anatomical_structure Endocrinology Reproductive Medicine Receptors FSH Gonadotropin receptor Female Seasons Gonadotropin Follicle-stimulating hormone receptor hormones hormone substitutes and hormone antagonists Gonadotropins |
| Zdroj: | Biology of reproduction. 78(2) |
| ISSN: | 0006-3363 |
| Popis: | Previous studies have provided evidence for a paracrine interaction between pituitary gonadotrophs and lactotrophs. Here, we show that GnRH is able to stimulate prolactin (PRL) release in ovine primary pituitary cultures. This effect was observed during the breeding season (BS), but not during the nonbreeding season (NBS), and was abolished by the application of bromocriptine, a specific dopamine agonist. Interestingly, GnRH gained the ability to stimulate PRL release in NBS cultures following treatment with bromocriptine. In contrast, thyrotropin-releasing hormone, a potent secretagogue of PRL, stimulated PRL release during both the BS and NBS and significantly enhanced the PRL response to GnRH during the BS. These results provide evidence for a photoperiodically modulated functional interaction between the GnRH/gonadotropic and prolactin axes in the pituitary gland of a short day breeder. Moreover, the stimulation of PRL release by GnRH was shown not to be mediated by the gonadotropins, since immunocytochemical, Western blotting, and PCR studies failed to detect pituitary LH or FSH receptor protein and mRNA expressions. Similarly, no gonadotropin receptor expression was observed in the pituitary gland of the horse, a long day breeder. In contrast, S100 protein, a marker of folliculostellate cells, which are known to participate in paracrine mechanisms within this tissue, was detected throughout the pituitaries of both these seasonal breeders. Therefore, an alternative gonadotroph secretory product, a direct effect of GnRH on the lactotroph, or another cell type, such as the folliculostellate cell, may be involved in the PRL response to GnRH in these species. |
| Databáze: | OpenAIRE |
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