Expression of growth hormone gene in the head kidney of gilthead sea bream(Sparus aurata)

The presence of growth hormone (GH) mRNA in the head kidney of gilthead sea bream (Sparus aurata) was assessed by reverse transcription and polymerase chain reaction (RT-PCR). Reverse transcription was made with oligo-dT prim ers, and a single cDNA band (435 bp) corresponding in length to the distanc e between two specific GK primers was obtained. No corresponding product wa s seen using liver and brain RNA samples. The amplified DNA hybridized spec ifically with a pituitary GH probe after Southern transfer to nylon membran es. The identity of this DNA fragment was further confirmed by sequencing a nested PCR product (343 bp). This finding supports the hypothesis that the immune system in both higher and lower vertebrates is an extrapituitary si te for the expression of GH, which may serve as an autocrine/paracrine fact or in immunomodulation. (C) 1999 Wiley-Liss, Inc.