The effect of hematoporphyrin and light on human platelets. II. Uptake of hematoporphyrin

A linear relationship was demonstrated between the reciprocals of the concentration of free hematoporphyrin and the moles of hematoporphyrin taken up by the platelet in the dark. radiated platelets took up more hematoporphyrin than did controls; this increase in uptake was accounted for by the movement of the dye across the damaged membrane of the cell. platelets irradiated at 4°c remained impermeable to hematoporphyrin until warmed to 37°c. during the initial three to four minutes of exposure to light at 37°c, there was no additional uptake of hematoporphyrin by platelets in comparison to controls. between six to ten minutes irradiation, the uptake of hematoporphyrin increased linearly with the log time of irradiation. thereafter, no further uptake occurred. a further increase in uptake of dye was demonstrated by both control and irradiated platelets at a reduced ph. this study enables a correlation to be made between the effects of hematoporphyrin on the platelet and the uptake of this agent by the platelet.