Multiparameter flow cytometry. Part I: Application in analysis of the cell cycle

During the past six years, new flow cytometric techniques, designed to measure other cell features in addition to DNA content, were developed in our laboratory. Specifically, the techniques for cellular RNA content and for simultaneous measurement of RNA and DNA content, detection of the incorporation of the thymidine analog 5 bromodeoxyuridine (BUdR) and analysis of nuclear chromatin structure, as reflected by the stability of DNA in situ to heat or acid, were introduced and then applied in a variety of cell systems. More recently, a new mitochondrial probe, rhodamine 123, was applied to analyse the cell metabolic state in addition to the cell cycle. The data yielded new information on the functional state of individual cells in relation to their position in the cell cycle. As a result, a new subdivision of the cell cycle was proposed. Based on this multiparameter classification, cells could be subdivided into 13 functionally distinct compartments. In this review, we describe briefly the new flow cytometric techniques and discuss results obtained on numerous cell systems which provided a base for the proposed subdivision.