Tricyclic antidepressant-induced lipidosis in human peripheral monocytes in vitro, as well as in a monocyte-derived cell line, as monitored by spectrofluorimetry and flow cytometry after staining with Nile red.

Human mono- and lymphocytes from peripheral blood and the monoblastoid cell line U-937 were used in this in vitro study of drug-induced lipidosis. Mono- and lymphocytes were exposed for 4 days to three different tricyclic antidepressants (TCAs), imipramine (25 microM), clomipramine (10 microM) and citalopram (80 microM). The lipophilic fluorophore Nile red, which stains intracellular lipid structures selectively, was used as a lipid probe. Fluorescence microscopy, spectrofluorimetry and flow cytometry were used to detect cellular lipidosis, as verified by electron microscopy. Our results demonstrate that imipramine, clomipramine and citalopram induce lipidosis in monocytes and U-937 cells, but not in lymphocytes. An accurate quantitation of induced intracellular lipidosis can be achieved by spectrofluorimetric and flow cytometric analysis.