pH-Dependent Changes in the Mechanisms of Transport of Chlorine e6 and Its Derivatives in the Blood.

We studied the effects of medium pH on steady-state distribution of chlorine e6 and its derivatives between the main transport proteins of human blood plasma. The decrease in medium pH from weakly alkaline (pH 7.4) to acid (pH 5.0) was followed by an increase in relative affinity of chlorines to lipoproteins and reduced their affinity to serum albumin. pH-Dependent changes in the parameters of distribution of photosensitizers between the plasma and blood cells was revealed. We discussed the role of charge and polarity degree of photosensitizer molecule in the mechanism of binding to serum albumin. A possible role of changes in hydrogen ion activity in the processes of selective accumulation of chlorines by tumor cells is discussed.

[Distribution of porphyrin sensitizers among protein and cellular blood elements]. / Raspredeleniie porfirinovykh sensibilizatorov mezhdu belkovymi i kletochnymi élementami krovi.

The distribution of porphyrin pigments between plasma proteins and blood cells was studied. It was shown that the relative fraction of sensitizer bound by blood cells changed significantly depending on the physicochemical features of pigment molecules. This parameter strongly correlates with porphyrin polarity. Polar watersoluble tetraphenylporphin derivatives, chlorine e6 and hematoporphyrin are bound by plasma proteins only. The decrease in pigment polarity by substitution of polar side groups results in a drastic increase of pigment affinity to blood cells. The binding of extremely apolar pigments by cells in blood occurs for a long period of time, probably as a result of a low rate of pigment redistribution between serum proteins and cellular membrane. The data obtained show that blood cells may be involved into the control of pigment transport and distribution in organism during photodynamic therapy. The parameters of porphyrin distribution between plasma proteins and cells in blood are of certain importance when the pharmacokinetic behavior of various sensitizers is compared.