Binding of hematoporphyrin to synchronized cells from the line NHIK 3025

The binding of hematoporphyrin (HP) to human cells of the line NHIK 3025 has been studied with the aid of microfluorometry. HP is concentrated within cells when present in Hank's balanced salt solution in the concentration range 10(-5)--3 x 10(-3) M. The time course of binding is biphasic with a rapid initial binding and a slower accumulation at times longer than 30 min. The amount bound to HP increases linearly as the cells proceed through the cell cycle and is doubled from early G1 to late G2.