RESUMO
Some specific functions are often localized to unique cellular types or structures in organs such as kidney, brain, blood, and endocrine glands. As a result, it is not ucommon that gene producta, although heavily expressed in some cell type within these organs, ultimately appear as low abundance products when total RNA is probed, resulting in decreased power of the conventional Northern blot analysis. To study gene expression in these circumstances, more sensitive techniques like RNAse protection assay and quantitative or semi-quantitative PCR strategies have been developed. In the present study, we provede a detailed descriptio of the semiquantitative PCR strategy in our laboratory. Using specific primers to amplify fragments from the neuronal isoform of the nitric oxide synthase and the thiazide-sensitive Na+:Cl- contransporter (low abundance messages in the kidney), we show that the semi-quantitative PCR strategy is a valuable tool when low abundance messages are to be studied