Simultaneous quantification of APP and tau mRNA by RT-PCR.

We describe here a method for simultaneous relative quantitation of APP and tau expressions in rat muscle using polymerase chain reaction combined with reverse transcription. The target mRNAs were coamplified with an internal control, glyceraldehyde-3-phosphate dehydrogenase (G3PD). The amplified products were measured with a laser image analyzer, and the values were plotted against the cycle number. In the exponential phase of amplification, the linearity and reproducibility of RT-PCR demonstrate identical efficiencies of cDNA synthesis and PCR amplification for APP, tau and G3PD. These results suggest that in the exponential phase of amplification, a relative quantitation of target mRNAs could be accomplished by normalization with internal control. Preliminary experiments indicate that the expressions of both APP and tau in rat muscle were first increased and then decreased by chronic intoxication with chloroquine.