Evidence for arylalkylamine N-acetyltransferase (AANAT2) expression in rainbow trout peripheral tissues with emphasis in the gastrointestinal tract.

In fish, melatonin is reported to be produced mainly in the pineal organ, but there is also evidence for the presence of melatonin in a number of extrapineal sites where it could act as an intracellular mediator or paracrine signal. The present study use the reverse transcription-polymerase chain reaction (RT-PCR) to evaluate the expression of the enzyme arylalkylamine-N-acetyltransferase (AANAT2), which catalyzes the limiting step for melatonin synthesis, in different peripheral tissues of rainbow trout, with emphasis in the gastrointestinal tract (GIT). The results show AANAT2 gene expression in almost all peripheral tissues tested, including gills, kidney, muscle, skin, liver, Brockmann bodies, gall bladder, spleen and GIT, but not in adipose tissue.