Effect of hexavalent chromium on eukaryotic plasma membrane studied by EPR spectroscopy

Abstract

The effect of Cr(VI) anion on an ergosterol-producing strain of eukaryotic yeast Candida albicans and its mutant with ergosterol-less membrane was studied with EPR spectroscopy. 5- and 14-doxyl stearic acid spin probes were used to label the protoplast membrane after removal of the cell wall. In control experiments, the mutant strain exhibited larger rigidity in the membrane than its parental strain. Addition of Cr(VI), at a minimum inhibitory concentration of 0.6 mM, increased the rotational mobility of the spin labels significantly and decreased the temperature of the structural changes in both strains, in the temperature range between 0 and 30 degrees C. The ergosterol-less mutant, having a membrane composition with increased polyunsaturated fatty acid content, exhibited higher Cr(VI) sensitivity. Treatment of the membrane with Cr(VI) for 10 min already resulted in an increase in membrane fluidity. An EPR signal of Cr(V) was detected which reached maximum amplitude after 120 min of treatment with Cr(VI). Further chemical reduction of Cr(V) in the absence of extracellular Cr(VI) led to a lack of detectable paramagnetic chromium intermediates within 200 min.

Chromate tolerance caused by reduced hydroxyl radical production and decreased glutathione reductase activity in Schizosaccharomyces pombe

“…The facilitated diffusion of CrO 4 2-into the cells started immediately after CrO 4 2-addition (BELÁGYI et al 1999). After pretreatment of S. pombe cultures with 250 µM K 2 Cr 2 O 7 for 120 min (BELÁGYI et al 1999), the chr1-66T mutant accumulated half as much Cr(VI) as did its parental strain (data not presented).…”

“…After pretreatment of S. pombe cultures with 250 µM K 2 Cr 2 O 7 for 120 min (BELÁGYI et al 1999), the chr1-66T mutant accumulated half as much Cr(VI) as did its parental strain (data not presented). The time-course of Cr(V) formation and reduction monitored by EPR spectroscopy indicated that both strains reduced Cr(VI) to Cr(III) through Cr(V), but the elimination of Cr(V) in the Cr(VI)-tolerant chr1-66T mutant was much slower than in 6chr + cells (Fig.…”

“…The in vivo generation and reduction of Cr(V) in S. pombe was followed by electron paramagnetic resonance (EPR) spectroscopy, as described elsewhere (BELÁGYI et al 1999, PESTI et al 2002. EPR spectra were recorded on an ESR 300E spectrometer (BRUKER, BIOSPIN, Germany).…”

Chromium picolinate positively influences the glucose transporter system via affecting cholesterol homeostasis in adipocytes cultured under hyperglycemic diabetic conditions

“…Several findings suggest that trace elements, e.g., iron, copper, zinc, selenium, chromium, cadmium, mercury and lead may influence membrane fluidity. In particular, hexavalent chromium (Cr 6+ ), which is well recognized to pose an environmental health risk, has been shown to increase membrane fluidity [50]. Consistent with this membrane change having an insulin-like action on glucose transport, hexavalent chromium significantly stimulates glucose uptake into rat adipocytes [39].…”

Extra-cellular chromate-reducing activity of the yeast cultures

“…It was demonstrated that ergosterol-less mutants with a modified plasma membrane structure exhibit Cr(VI) changed sensitivity [21]. The modified tolerance of the mu-tant cells to chromate is accompanied with the changes in Cr(VI) uptake and chromium bioaccumulation [22].…”