Journal
GENERAL AND COMPARATIVE ENDOCRINOLOGY
Volume 165, Issue 1, Pages 60-71Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.ygcen.2009.06.001
Keywords
Kisspeptin-10; Kisspeptin receptor; Growth hormone; Prolactin; Gonadotropin; Laser capture microdissection; Pituitary cells; Goldfish
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Funding
- Research Grant Council (Hong Kong)
- National 973 Program (China)
- University Research Committee (University of Hong Kong)
- School of Biological Sciences (University of Hong Kong)
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Kisspeptin, the product of Kiss1 gene, is a novel regulator of the gonadotropic axis. In mammals, its stimulatory effect on gonadotropin secretion is well documented and mediated mainly by hypothalamic release of gonadotropin-releasing hormone. Although the pituitary actions of kisspeptin have been reported, the effects of kisspeptin on gonadotropin release via direct action on pituitary cells are still controversial. Using goldfish as a model, here we examined the direct actions of kisspeptin on pituitary functions in modern-day bony fish. As a first step, the structural identity of goldfish Kiss1 was established by T/TRACE and Kiss1 transcript was shown to be widely expressed in various tissues in goldfish. At the pituitary level, Kiss1 receptor (Kissi1r) expression was detected in immuno-identified gonadotrophs, lactotrophs, and somatotrophs. Kiss1 transcript was also located in goldfish somatotrophs but not in lactotrophs or gonadotrophs. In parallel studies, goldfish kisspeptin-10 was synthesized and used to test the pituitary actions of kisspeptin in vitro. In goldfish pituitary cell cultures, 30-min incubation with kisspeptin-10 increased basal release of luteinizing hormone (LH), prolactin (PRL), and growth hormone (GH). Transcript expression of LH, PRL, and GH were also elevated by prolonging kisspeptin-10 treatment to 24 h. These results taken together suggest that kisspeptin via Kiss1r activation can act directly at the pituitary level to trigger LH, PRL, and GH secretion and gene expression in goldfish. Our finding of Kiss1 expression in somatotrophs also rises the possibility that kisspeptin may be produced locally in the fish pituitary and serve as an autocrine/paracrine regulator. (C) 2009 Elsevier Inc. All rights reserved.
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