Induction of spermatogenesis in Japanese eel by recombinant goldfish gonadotropins |
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| Authors: | Youichi Hayakawa Hidekazu Nagaya Hiroki Kaki Komei Hotta Makito Kobayashi |
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| Institution: | (1) Department of Life Science, International Christian University, Mitaka Tokyo, 181-8585, Japan;(2) Katakura Industries Co. Ltd, Sayama Saitama, 350-1332, Japan;(3) Marine Ecology Research Institute, Kashiwazaki Niigata, 945-1007, Japan |
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| Abstract: | We previously demonstrated the biological activities of single-chain recombinant gonadotropins (scGTHs) of goldfish Carrassius auratus follicle-stimulating hormone (scFSH) and luteinizing hormone (scLH), produced by a baculovirus–silkworm larvae system, by
using in vivo bioassays with some fishes including Japanese eel Anguilla japonica. Among the bioassays, we succeeded in induction of spermatogenesis of sexually immature male Japanese eels by both scFSH
and scLH, especially resulting in the occurrence of spermatozoa in scLH-administered males. However, those recombinant hormones
did not induce enlargement of testes. In order to further confirm the potency of recombinant GTHs for use in aquaculture species,
we administered scFSH and scLH to males of Japanese eel at higher dosage and frequency (eight times with 2–5 days interval)
than those of the previous study (five or six times with 7 days intervals), including combination of scFSH and scLH administration
(scFSH–scLH). Gonadosomatic indices (GSI) of scLH- and scFSH–scLH-administered males were larger than those of initial control
males and of control males that were injected with saline. Enlargement of testes was also confirmed by measurement of testicular
lobe size in scFSH-, scLH-, and scFSH–scLH-administered males. By histological observation, occurrence of spermatozoa was
confirmed in scLH- and scFSH–scLH-administered eels. Although milt production was not induced, higher dosage and frequency
of scGTH administration was effective in promoting testicular development of immature eels. Thus, single-chain fish GTHs produced
by the baculovirus–silkworm larvae system could be a useful tool for promotion of gonadal maturation in aquaculture fishes. |
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| Keywords: | FSH Goldfish Gonadotropin Japanese eel LH Recombinant hormone Single-chain Spermatogenesis |
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