[The effects of antitumor agents of croton alkaloids and cisplatin on human red blood cell membranes].

The effects of antitumor drugs of croton alkaloids (CA) extracted from croton, and cisplatin on the structure of human erythrocyte membrane and bovine serum albumin (BSA) were studied with the techniques of circular dichroism, fluorescence spectroscopy and ultraviolet absorption. From measuring circular dichroism between 200-240nm, it was found that the alpha helix of membrane and BSA increased after CA addition. Cisplatin was also found effective in altering membrane alpha helical content. BSA showed a loss of fluorescence intensity and a blue-shift of emission peak after CA addition. The florescence quenching and peak shift may reflect the movement of tryptophan to a more nonpolar environment (the hydrophobic portions of proteins). This is consistent with the increase in helicity of BSA in the presence of CA. From measuring fluorescence polarization of membrane, it was found that membrane fluidity decreased in the presence of CA, but did not change in the presence of cisplatin. The results indicate that both CA and cisplatin lead to alterations in the secondary structure of membrane protein. The conformation change in membrane protein may account for the pharmocological effect of CA and cisplatin.