镉与离体大鼠肾微粒体膜的相互作用

Interaction of Cd^(2+) with membranes of rat renal microsome in vitro

本文利用荧光探剂ANS研究了Cd^(2+)与大鼠肾微粒体膜的相互作用。结果发现,Cd^(2+)能明显增加与膜结合的ANS荧光强度和荧光偏振度。用ANS荧光滴定法研究证实Cd^(2+)能降低膜ANS复合物的表观解离常数(Kd)和增加膜上ANS的结合位点数(n)。上述结果提示,Cd^(2+)能降低大鼠肾微粒体膜流动性和膜表面负电荷密度。

Cadmium (Cd2+) has been recognized as a toxicologically important environmental contaminant. Kidney is its major target, and the mechanism of the cytotoxicity is not well known. In this paper, effects of Cd2+ on the lipid fluidity and surface negative charge density of the membranes of rat renal microsome were investigated in vitro by using 8-anilino-1-naphthalene-sulfonic acid (ANS) as a fluorescence probe. Cd2+(0.01-l mmol/L) increased the fluorescence intensity and polarization of the ANS-membrane complex. No shift in emission spectra was observed in the membranes treated with 1 mmol / L Cd2+. By means of ANS fluorometric titration, it was observed that after the treatment with 1 mmol / L Ca2+ the ANS-binding sites on the membranes increased about 22% and the apparentdissociation constant of the ANS-membrane complex decreased by 94% compared with the control. The enhancement of fluorescence intensity is due to an increase in the ANS binding site on the membrane, but not to an increase in the quantum yield of ANS on it. These findings suggest that Cd2+ significantly decreases the lipid fluidity and surface negative charge density of the membranes of the rat renal microsome in vitro. The change in lipid fluidity caused by Cd2+ is subsequent to that in the surface negative charge density of the membrane.