Regulation of 5-aminolevulinic acid-dependent protoporphyrin IX accumulations in human histiocytic lymphoma U937 cells.

The aim of the present work is to clarify the mechanism(s) that regulates the accumulation of protoporphyrin IX (PpIX) in human histiocytic lymphoma cell line U937 incubated with 5-aminolevulinic acid (ALA). Biosynthesis and accumulation of PpIX in the cells was determined after incubation with 0.1-5 mM ALA using a flow cytometric technique.