Co-expression of somatolactin mRNAs in the pituitary gland of gilthead sea bream

Abstract.

The expression of mRNAs of the two types of somatolactin which have been found, up to the present, in the pituitary of gilthead sea bream (Sparus aurata) have been analyzed by in situ hybridization (ISH). The method of non-radioactive ISH, which we optimize in this study, uses oligonucleotides labelled in the 5′ end with biotin or dioxygenin as probes. This allows simple and double ISH of high specificity and sensitivity to be performed. The distinct somatolactin oligoprobes used present a strong signal fundamentally in the pars intermedia of the pituitary gland. For the first time we present cells that co-express both the forms of mRNA mentioned above. Moreover, after studying three groups of different sizes, produced by asynchronic growth of the gilthead sea bream in industrial cultivation, we did not find qualitative differences in the levels of expression of the somatolactin gene.