Effects of MCH and GnRH on Somatolactin secretion from organ-cultured pituitary of the cichlid fish Cichlasoma dimerus

CANEPA M; POZZI AG; MAGGESE MC; VISSIO PG

Pinamar, Buenos Aires

Congreso; 10th Congress of Panamerican Association for Biochemistry and Molecular Biology. 20th Annual Meeting Argentine Society for Neurochemistry; 2005

Sociedad Argentina de Investigaciones en Bioquimica y Biología Molecular. Sociedad Argentina de Neuroquimica

Somatolactin (SL) is a hormone belonging to the GH/PRL family, produced in the pars intermedia of teleost pituitary. Its function is uncertain and there is very scarce information on the regulation of SL secretion. Two forms of SL were detected in C.dimerus: 32 kDa, a glycosylated form and 28 kDa, a deglycosylated faster migrating form. Our trials using double immunohystochemistry showed a close association between SL cells and both GnRH and MCH fibers. Analysis by immunoblots of in vitro culture of pituitaries showed that GnRH and MCH stimulated above the basal level the SL release in a dose-dependent manner. There was no difference in the rates of release between the two forms of SL. When the pituitaries were first stimulated with MCH, an increase in the SL release was observed. When MCH stimulus was withdrawn and after reaching the basal level of secretion again, a new increase in SL was observed with GnRH addition. The pituitaries that did not receive either GnRH or MCH stimulation showed a decrease in SL secretion on 2nd day of culture. These results demonstrated that MCH and GnRH stimulated the SL release. Like other pituitary hormones, it is likely that SL is under hypothalamic control and could be implicated in diverse areas including background adaptation and reproduction.