Sequence analysis of Somatolactin from Cichlasoma dimerus SL and its relation with MCH

CÁNEPA, MAXIMILIANO; POZZI, ANDREA; CARCAGNO, ABEL; MAGGESE, MARÍA CRISTINA; VISSIO, PAULA

SAINT MALO FRANCE

Simposio; 8th international Symposium on reproductive physiology of fish; 2007

Joint Research Unit for Fish Physiology, Biodiversity and the Environment (SCRIBE) of the INRA Research Centre of Rennes, the CNRS (Rennes) and IFREMER (Brest).

BACKGROUND: There is increasing evidence that somatolactin (SL) is a multifunctional hormone. In Cichlasoma dimerus, a Southamerican cichlid fish that shows dramatic changes in body coloration during sexual activation, we found clear evidence of a possible involvement of SL together with melanocyte stimulating hormone (MSH) and melanin concentrating hormone (MCH),in background colour adaptation. However, there is scarce information on the regulation of SL release. This study is focused on the relation between SL and the neuropeptides MCH and GnRH. In addition we report the characterization of partial C. dimerus SL (cdSL) cDNA. METHODS: Adult fish were processed for double-labelled immunohistochemistry (IHC) in order to analyze a possible close association between SL, MCH and GnRH. In addition, pituitary glands were removed from C. dimerus and cultured during 4 days in 96 wells plate with L15. On day 1: Medium was removed and fresh medium was added with or without GnRH (0.01 to 10 μM) or MCH (0.01 to 10 μM); after 24 hr the medium was removed. In pituitaries treated with MCH fresh medium was added for recovery of hormonal release; on day 3, medium with or without GnRH (1μM) was added and finally, after 24 hr mediums were remove. Each culture medium removed was stored frozen for further analysis by western blot. Furthermore, degenerate primers were used to characterize, by PCR and further sequence analysis, the internal region of cdSL cDNA from pituitary gland. RESULTS: We found a clear morphological association between MCH fibers, originating from the nucleus lateralis tuberis (NLT), and SL cells. Besides, we found GnRH fibers in association with SL cells. O the other hand, we observed in the NLT, GnRH fibers in close association with MCH soma and fibers. The analysis by immunoblots showed that after 24hs with MCH or GnRH, SL release increases significantly in a dose-dependent manner (p