Expression of an inducible nitric oxide synthase gene in rainbow trout Oncorhynchus mykiss

Using oligonucleotide primers based on mammalian nitric oxide synthases (SO S), expression of an inducible NOS (iNOS) gene was detected in head kidney and gill tissue of bacterially-challenged rainbow trout. Three overlapping fragments were amplified by RT-PCR and used to construct a contiguous seque nce of 1410 bp, with high nucleotide homology to iNOS in birds (61%) and ma mmals (57-59%). The nucleotide sequence translated in one reading frame to produce a partial peptide containing 470 amino acids, with 69-71% amino aci d homology with mammalian iNOS, 81% homology with chicken iNOS and 85% homo logy with a partial (492 bp) goldfish iNOS sequence. In vitro stimulation o f head kidney macrophages with LPS also induced expression of the trout iNO S RNA. with optimal expression seen using 20 50 mu g/ml LPS at 2 h to 6 h p ost-stimulation. The evolutionary and functional significance of the trout iNOS sequence are discussed. (C) 1999 Elsevier Science Ltd. All rights rese rved.