Molar quantification of specific messenger ribonucleic acid expression in northern hybridization using cRNA standards

Procedures were developed for estimation of specific mRNA expression as measured by Northern hybridization in terms of moles of message present in tissue samples. These procedures use an externally added cRNA pseudomessage standard with cRNA concentration curves for both the standard and the message of experimental interest in order to convert hybridization signals into moles of message per milligram wet weight of tissue. We present a test of these procedures using hybridization to the message for the glucocorticoid-inducible enzyme tyrosine aminotransferase in rat liver. These procedures accommodate for variations in both RNA yield and hybridization signal intensities, and are applicable to the measurement of changes in message expression of twofold or more using triplicate determinations of a single RNA preparation. This approach allows for the integration of data from many individual hybridization experiments, and may be useful in experimental situations that involve population studies and/or long-term comparisons of treatments.