Technology Review: Molecular Approaches for Quantifying DNA Synthesis and Cell Proliferation During Rodent Bioassays

Abstract

The induction of sustained, chemically-induced regenerative hyperplasia during rodent bioassays may result in carcinogenesis. Hence, accurate measurement of replicative DNA synthesis and cell proliferation in putative target organs during acute and subchronic assays will aid in dose selection for chronic studies; and assessment of cell proliferation rates during chronic bioassays will aid in the interpretation of results and in risk assessment. Histopathology is the traditional method for assessing hyperplasia and will continue to be of paramount importance. However, quantitative molecular approaches for assessing rates of DNA synthesis and mitogenesis in many cases extend and complement histopathological examinations. Three of these methodologies, incorporation of radiolabeled thymidine into DNA, incorporation of bromodeoxyuridine into DNA, and measurement of proliferating cell nuclear antigen, are discussed in this review. Also, a relatively new technology, the use of flow cytometry to measure the incorporation or binding of fluorescent dyes, is discussed. The theoretical basis and applications for each of the procedures are discussed and the advantages and disadvantages of each are outlined. The method of choice depends upon the objectives of the experiment, the tissues to be examined, and the availability of specialized instrumentation. Molecular quantitation of mitogenesis is expected to assume an increasingly prominent role in the conduct and interpretation of rodent bioassays.

Key Words: :

• Molecular quantitation
• Mitogenesis
• Deoxyribonucleic acid synthesis
• Carcinogenesis