RAPID RNA ISOLATION WITHOUT THE USE OF COMMERCIAL KITS - APPLICATION TO SMALL TISSUE SAMPLES

We describe an adapted version of the Chomczynski and Sacchi [Anal Bio chem (1987) 162.156-159] RNA isolation procedure that can be performed in less than 1 h on small (<15 mg tissue samples, using commonly avai lable reagents. Our modifications included: (1) one rather than two pr ecipitation steps in the aqueous phase with 99% ethanol and (2) elimin ation of the 1-h incubation step at -20 degrees C. Our adaptations res ulted in RNA yield (mu g/mg of tissue) and purity (260/280 nm ratios) comparable to those of the original procedure. Furthermore, the isolat ed RNA was successfully utilized in reverse transcriptase-polymerase c hain reaction assays, suggesting that it was essentially free of carry -over contaminants that could inhibit enzymatic reactions. When tested on tissue sample sizes of 7-12 mg. our adapted procedure allowed the recovery of enough total RNA for use in techniques such as Northern bl ot analysis. Our modified technique is therefore an inexpensive altern ative to commercially available kits when isolating good-quality RNA f rom very small tissue samples, such as those obtained from needle biop sies.