Introduction

Cell cultures are frequently used in biological studies because it is possible to control closely the experimental conditions. Several different in vitro systems are currently used in biochemical and morphological studies of the effects of growth factors, teratogens, toxic substances and heavy metals on cell physiology and morphology. Changes in the elemental composition of the cells can be measured by X-ray microanalysis (XRMA) which, combined with biochemical or morphological techniques, contributes to an understanding of the role of ions in physiological and pathological processes. XRMA has several important advantages over more widely used analytical methods, e.g. atomic absorption or flame spectrophotometry (Wroblewski et al., 1989). It allows analysis of individual cells in a heterogeneous cell population, which cannot be achieved by the above mentioned methods. Cell cultures can be relatively easily prepared for XRMA without the use of costly equipment such as a cryostat or cryoultramicrotome. There is no need for dissection (compared to tissue samples) and the thickness of cultured monolayers, which is in the range of 5 μm, rarely exceeding 10 μm, improves conditions for good fixation by quench freezing. Due to the ease of specimen preparation, several XRMA investigations have been carried out on cultured cells (Lechene, 1989; Saubermann & Stockton, 1988; Wroblewski et al., 1983b; Wroblewski & Roomans, 1984, Wroblewski et al., 1987; Zierold, Gerke & Schmitz, 1989). Intracellular element localisation, epithelial transport, dynamic processes and pathological accumulation of extraneous and endogenous material have been studied.