“ Somatolactin: a pituitary hormone involved in teleost background adaptation”. Cánepa MM, Pandolfi M, Maggese MC y Vissio PG.

CÁNEPA, MAXIMILIANO; PANDOLFI, MATÍAS; MAGGESE, M. CRISTINA; VISSIO, PAULA G.

Castellón, España

Simposio; 5TH INTERNATIONAL SYMPOSIUM ON FISH ENDOCRINOLOGY.; 2004

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Somatolactin (SL) is a structurally-conserved pituitary hormone that belongs to the growth hormone/prolactin family. Although its biological function remains to be elucidated, several studies have indicated that SL is involved in various biological processes. This study is focused on the relation between SL and background adaptation in the cichlid fish Cichlasoma dimerus. 30 larvae and 30 juvenile fish were transferred into black or white tanks for 15 days. Larvae were then processed for SL immunohistochemistry (IHC) in order to determinate average cell area and number of immunoreactive (ir-) SL cells. Juvenile pituitaries were homogeneized and their amount of proteins was measured. Western Blot analysis was then carried out in order to determinate differences between SL contents in both experimental conditions. Differences in skin colour reflected the adaptation to the different backgrounds (black fish: BF and white fish: WF). The average area of ir-SL cells was significantly increased (P<0.05) in BF as was the average number of ir-SL cells per 7 µm section (27.390 ± 2.099 µm2 , 23 ± 3) in comparison to WF (16.613 ± 1.237 µm2 , 7 ± 1). Western Blot results were consistent with these data, showing a major SL expression in BF pituitary homogenates. Double IHC also showed a close association between MCH fibbers and SL cells in the pars intermedia. This fact, together with the observed difference in ir-SL cells between treatments, may reflect an involvement of SL in the physiological adaptation to different coloured backgrounds.