Microwave irradiation of paraffin-embedded tissue sensitizes the TUNEL method for in situ detection of apoptotic cells.

Apoptosis is a morphologically distinct form of programmed cell death that plays an important role in the growth regulation of a variety of tissues and also in the elimination of self-reacting immunocompetent cells. Several techniques for the qualitative and quantitative detection of this process have been established; recently, an in situ nick end-labelling technique based on the detection of DNA fragmentation, which is a molecular characteristic of apoptotic cell death, was described. Applying this method to paraffin sections of human tissues, sensitivity was observed to be inconsistently low with regard to the expected number of apoptotic cells. In the present study we show that irradiation of the tissue sections in 10 mM citrate buffer, pH 6.0, by microwaves at 750 W considerably enhances the sensitivity of this nick end-labelling technique.