Tissue distribution of bacteriochlorin a labelled with 99mTc-pertechnetate in hamster Greene melanoma.

Bacteriochlorin a (BCA), a new photosensitizer for photodynamic therapy, was labelled with 99mTc-pertechnetate following a method for the irreversible coupling of 99mTc-pertechnetate to proteins. Biodistribution studies were conducted in male Syrian Golden hamsters with hamster Greene melanoma implanted s.c. on both sides of the abdomen. After i.v. administration of 99mTc-pertechnetate-labelled BCA 17 tissue and fluid samples were analysed at time intervals ranging from 1 to 24 h. Technetium-labelled BCA showed a pronounced affinity for tissues belonging to the reticuloendothelial system. Peak activities, 1 h post-injection, were distributed as follows: lung, liver, spleen, urine > small intestine, kidney, blood, heart, stomach, large intestine > thyroid, tumour, bone, skin, muscle, eye >> brain. It is concluded that the technetium-labelled photosensitizer BCA does not accumulate selectively in neoplastic tissue.