PERCHLORIC ACID EXTRACTION AS A HISTOCHEMICAL TECHNIQUE

Abstract

Investigations have been carried out to determine the efficiency of cold perchloric acid in the differential extraction of RNA from tissues fixed in acrolein and Carnoy's fixative. It has been found that this reagent will selectively extract RNA from tissue without extracting or causing significant depolymerization of DNA. The DNA in the tissue is, however, denatured (i.e., its secondary structure is destroyed) and depurinized to a degree dependent upon the time of extraction. When the procedure was carried out at 4°C, there was no evidence of extraction of proteins, glycoproteins, or hipoproteins. Some phospholipid was extracted under these conditions. It is concluded that the cold perchloric acid technique for differential extraction of RNA from fixed tissues is useful and not subject to the faults often ascribed to it in the histochemical literature. The significance of loss of Feulgen and methyl green staining following prolonged PCA extractions is discussed in relation to the chemistry involved in DNA-methyl green binding and the Feulgen reaction. Abbreviations used: Perchloric acid = PCA Desoxyribonucleic acid = DNA Ribonucleic acid = RNA Trichloroacetic acid = TCA Thymine/adenine ratio = T/A Cytosine/guanine ratio = C/G Optical density = OD