ヘマトポルフィリン誘導体 (HpD) の取込みとその温度効果, および加温による殺細胞効果

抄録

The uptake of hematoporphyrin derivative (HpD) by Ehrlich ascites cancer cells was investigated with measuring of the fluorescence intensity of HpD bound to the cells at various temperatures. It was shown that there are two steps in the HpD binding process by the analysis of the HpD fluorescence emission pattern. (1) Weak binding mode : the fluorescence peak appeared at 617 nm in the early reaction time below 25 °C. (2) Stable binding mode : the fluorescence peak appeared at 630 nm even in the early reaction time above 30 °C and also in later time below 25 °C. Increased amount of HpD molecule was incorporated into the cencer cells at higher temperature and it was considered that the HpD uptake is mainly due to facilitated diffusion. The Arrhenius plots of logarithmic values of the initial velocity and the reciprocal of the absolute temperatures in HpD-uptake reaction was biphasic of which inflexion point being at 28.7 °C. From the plots, the lower activation energy corresponded to the weak binding and the higher one to the stable binding mode. It was considered that critical temperature correlates with the phase change of the membrane lipid to which HpD molecules bind.
Furthermore, it was found that the S and G₂ (+M) phase cells incorporated larger amount of HpD than the G₁ phase cells by the cytofluorometer determinations of the amounts of nuclear DNA (Hoechst 33258) and HpD on a single cells.
Survival curve analysis of the Ehrlich cancer cells in hyperthermia with or without pre-treatment with HpD administration reveald that both incorporated and membrane-bound HpD have a mild protective effect against hyperthermia. Nevertheless, it was suggested that the combination therapy of cancer cells by laser radiation after HpD administration plus hyperthermia might be more effective than that of each single treatment.