Photodynamic action of two hematoporphyrin derivatives on transport and intracellular metabolism of adenosine in hepatoma cells

The initial rate of adenosine uptake was markedly inhibited by HPD photosensitization. The inhibition of adenosine uptake depends on HPD concentration and irradiation time. At the dose of 10μg/ ml and irradiation for 10 min, the inhibitions of adenosine uptake by HPD (B) and HPD (Y) were 70 and 69%, respectively. At 5μg/ml and light exposure for 10 min, the incorporation of [3H]adenosine into acid-soluble and acid insoluble material of hepatoma cells were equally reduced. The phosphorylation of adenosine in hepatoma cells was not influenced by HPD plus light. This suggests that the reduced incorporation of [3H]adenosine in acid-soluble material is not due to the impairment of intracellular transformation, but due to the inhibition of adenosine transport at membrane level. From these results and our previous experiments, it is concluded that the cell membrane and the nucleoside transport process are very sensitive to HPD photo-dynamic action.