Tumour-localizing properties of porphyrins. In vivo studies using free and liposome encapsulated aminolevulinic acid.

1. Using different doses of free and liposome encapsulated aminolevulinic acid (ALA) (between 2 and 8 mg/animal), given i.p., s.c. and intra-tumoural (i.t.), in vivo porphyrin synthesis by tumour, red blood cells (RBC) and different organs from tumour-bearing mice (TBM) and normal mice (NM) at different times, up to 24 hr after ALA administration, was examined. 2. It was found that by giving entrapped ALA, at a dose of 6 mg/animal (or 200 mg/kg wt), after 10 hr, a high level of porphyrin accumulation in the tumour was produced (7 micrograms/g tissue). Low synthesis occurred in muscle, lung, brain, RBC and skin; in spleen, kidney and liver synthesis is significant after 10 hr, but after 24 hr returned to normal values in the spleen and to about 2-3 micrograms/g tissue in the kidney and liver. 3. The tumour/skin porphyrin concentration ratio after 10 hr was nearly 30, the highest so far reported. 4. These results support our previous in vitro findings, indicating that free or encapsulated ALA might be used for early diagnosis of cancer and in photodynamic therapy.