Rapid analysis of DNA strand breaks in soft tissues

A technique was developed to measure rapidly DNA strand breaks in soft tissues. This method measured the rate of alkaline unwinding of DNA, which was proportional to strand breakage. Alkaline unwinding of DNA was done by treating tissue homogenates with NaOH. Single-stranded DNA was removed by extraction with aqueous phenol. DNA unwinding was quantitated by measuring the remaining double-stranded DNA. Using the described technique, a dose-effect relationship was observed between N-nitrosodimethylamine (NDMA) and alkaline unwinding of mouse liver DNA.