Fig. 5. Tissue distribution of intestine-type NaPi (I) and pyloric caeca-type NaPi (PC) cotransporter mRNA in rainbow trout consuming a normal (sufficient) P diet. Total RNA was reverse-transcribed using oligo-dT₂₀ primer, and PCR-amplified for 14 cycles for both intestine-type NaPi (I-NaPi) and pyloric caeca-type NaPi (PC-NaPi), or 7 cycles for beta-actin. The PCR products were Southern-transferred onto a nylon membrane, and probed with ³²P-labelled cDNA (a mixture of I-NaPi, PC-NaPi and beta-actin cDNA, equimolar basis). Three fish were examined, and the representative blot is shown above. Specific primers, designed from a unique region, amplified either I-NaPi or PC-NaPi, but not both.