Practical applications of the microphotometric quantification of histoenzyme reactions

There are many histochemical reactions which can be used for the accurate topographic detection of enzymes in tissues. There are also many reports of applications of these techniques in which the results have been evaluated subjectively. However, only a few of these methods have been the subject of quantification, using different methodologies, most of them based on microphotometry. A critical analysis of these procedures has generally shown that they are valid either relatively or at an absolute level. Nevertheless, the routine application of these methods is not as widespread as one might expect. In this paper, the methodological developments that have taken place in the histochemical assay of some enzymes by microspectrophotometry are reviewed briefly. The enzymes include acid phosphatase, non-specific esterase, succinate dehydrogenase and cytochrome oxidase. These methods have given consistent and useful results when applied to our experimental models of irradiated skin, and thus seem useful for various other applications. The reasons why there have been so few applications for quantitative histochemistry are also discussed together with possible ways of making its use more general.