The aim of this work was to look for the stress protein P
33, during long-term growth of human EUE cells in a hypertonic medium, with a polyclonal antibody against P
33 produced in rabbit, and detectable in cells by both light and electron microscopy, using fluorescein-, peroxidase-anti-peroxidase- and gold-indirect immunolabelling. P
33 was found to be mostly located in the cytoplasm, without apparent association with subcellular organelles; a slight, but significant, labelling was also observed in the nucleus. Dual parameter flow cytometric measurements of fluorescein-immunolabelled P
33 and DNA content (after propidium iodide staining) showed that the amount of P
33 increased progressively with increasing times of growth in a hypertonic medium in all phases of the cycle. Therefore there is no direct relationship between the increase of the P
33 and the exit of cells from the cycling compartment that occurs in a hypertonic environment.
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