EFFECT OF SEASONAL ACCLIMATIZATION ON THE EXPRESSION OF THE CARP TRANSCRIPTION FACTOR PIT-1

We isolated a clone comprising four exons of the carp Pit-1 gene. Usin g synthetic oligonucleotide probes derived from the carp Pit-1 sequenc e Pit-i expression was assessed by in situ hybridization in pituitary sections from summer- and winter-acclimatized carp. Semiquantitative a nalyses of the hybridization signals revealed a significant higher Pit -1 expression in the proximal pars distalis (PPD) and pars intermedia (PI) of the pituitary glands from summer-acclimatized carp, compared t o the winter-acclimatized fish. In both adaptive states, relative to t he PPD and PI, only a basal Pit-1 expression was detected in the rostr al pars distalis. Thus, during seasonal acclimatization of an euryther mal fish, Pit-1 seems to be involved in the mechanisms that underlie t he compensatory response. Key words: Pit-1, carp, acclimatization, fis h, gene expression.