Fig. 5. Tissue specificity of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (6PF-2K/F-2,6BPase), pyruvate kinase (PK), fructose-1,6-bisphosphatase (FBPase) and glucose transporter type 2 (Glut2) gene expression in food-deprived rainbow trout and fed rainbow trout with 20% carbohydrates (at 6h after feeding). Analysis by non-quantitative RT–PCR (N=2 fish per treatment). Ma, molecular mass marker phiX174 DNA/HaeIII (Promega, USA); N, negative control, i.e. RT–PCR reactions performed without RNA and with reverse transcriptase (other controls made with RNA and without reverse transcriptase were also performed to determine genomic DNA contamination; data not shown). L, liver; Mu, muscle; H, heart; B, brain; K, kidney; I, intestine. The exact lengths of the 6PF-2K/F-2,6BPase, PK, FBPase and Glut2 fragments (205bp, 300bp, 288bp and 222bp, respectively) were determined from known gene sequences. The quality of the first-strand cDNA used in each of the PCR assays was first confirmed by its ability to support the amplification of FBPase and 6PF-2K/F-2,6BPase cDNAs, and the failure to detect the presence of PK and Glut2 mRNA in certain tissues does not imply poor quality of RNA samples or a low-efficiency reverse transcription reaction.