Lipid fluidity of human and guinea-pig epidermal cells: temperature dependence in comparison to nonepidermal cells.

Abstract

Fluorescence polarization of lipophilic 1,6-diphenyl1,3,5-hexatriene (DPH) incorporated into cells yields information on the fluidity of cellular lipids being localized largely in cell membranes. Membrane lipid fluidity influences regulatory functions which take place at the membranes, e.g., signal transduction [4, 11, 12, 17, 19]. Differences in cell lipid fluidity have been found between normal and transformed cells of blood, liver, and thymus [4, 9, 17]. High levels of cholesterol, sphingomyelin, and protein as well as a high amount of saturated phospholipid acyl chains are known to coincide with low lipid fluidity. Aside from these chemical modulators, there .are physical factors involved such as temperature, hydrostatic pressure, pH, and membrane potential [17, 19]. By introducing the biophysical technique of DPH fluorescence polarization into the study of epidermal cells, we focussed on temperature-dependent alterations of the epidermal lipid fluidity. This investigation was stimulated by the fact that skin temperature, e.g., in humans, can vary between 20~ and 40 ~ C, adapting to environmental temperature, without damaging skin cells [16]. We compared the lipid fluidity of guinea-pig and human epidermal cells, normal human fibroblasts, and HT-1080 cells, a human fibrosarcoma cell line with epithelial growth pattern [15], within and beyond the physiological range of temperature. Epidermal cells were isolated from the ears of 2-month-old guinea pigs (Bor/DHPW-albino; Winkelmann breeding farm, D-4799 Borchen) and