title: Peripheral administration of Kiss1 pentadecapeptide induces gonadal development in sexually immature adult scombroid fish.
abstract: Kisspeptins have emerged as potent regulators of the reproductive brain-pituitary-gonad (BPG) axis. Our previous study demonstrated that the brain of the chub mackerel (Scomber japonicus), a scombroid fish, expresses two kisspeptin-encoding genes, kiss1 and kiss2, and exhibits sexually dimorphic expression profiles. Recent studies strongly suggest that teleost Kiss1 and Kiss2 precursors produce mature Kiss1-pentadecapeptides (Kiss1-15) and Kiss2-dodecapeptides (Kiss2-12), respectively. In light of the above, the present study evaluated the potency of synthetic peptides of Kiss1-15, Kiss2-12, and a GnRH analog (GnRHa) on inducing gonadal development in sexually immature adult chub mackerel. Synthetic peptides were administered subcutaneously through mini-osmotic pumps. On day 45 post-administration, gonadosomatic index (GSI) values (%) of male fish treated with Kiss1-15 (1.82) significantly increased in comparison to initial control (0.33), final control (0.49), Kiss2-12 (0.24), and GnRHa (1.13)-treated fish. Interestingly, the testis of all Kiss1-15 treated fish revealed spermiation, and were full of spermatozoa. These fish showed significantly higher levels of pituitary fshβ and Ihβ mRNAs and circulating 11-ketotestosterone. GnRHa treated fish also revealed the presence of few spermatozoa in the testis. In females, no significant changes in GSI values were found between treatments; however, Kiss1-15- and GnRHa-treated fish showed prominent signs of vitellogenic onset, with many early yolk oocytes in their ovaries. Interestingly, Kiss1-15-treated fish exhibited higher levels of pituitary fshβ and circulating estradiol-17β. These results indicate that peripheral administration of Kiss1-15 and GnRHa can induce gonadal development in sexually immature chub mackerel.
authors.affiliation: Laboratory of Marine Biology, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Sethu
authors.initials: S
authors.lastname: Selvaraj
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Ohga
authors.forename: Hajime
authors.initials: H
authors.lastname: Kitano
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Nyuji
authors.forename: Akihiko
authors.initials: A
authors.lastname: Yamaguchi
authors.forename: Michiya
authors.initials: M
authors.lastname: Matsuyama
mesh_terms: D000818:Animals; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D012739:Gonadal Steroid Hormones / Q000235:genetics / Q000378:metabolism; D059648:Kisspeptins / Q000494:pharmacology*; D008297:Male; D010473:Perciformes / Q000254:growth & development*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012741:Sexual Maturation / Q000187:drug effects*
chemical_list: D012739:Gonadal Steroid Hormones; D059648:Kisspeptins; D012333:RNA, Messenger