132-hydroxy bacteriopheophorbide a methylester specific uptake ratio in mice bearing lewis lung carcinoma

Abstract

Summary The ratio of the accumulated photosensitizer concentration to its injected dose is named the specific uptake ratio (SUR). Investigations on a photosensitizer's biodistribution using the parameter SUR offer a better understanding of the pharmacokinetic behaviours of different photosensitizers and render the comparison of different photosensitizers possible by overcoming the problem of using different sensitizer doses in different studies. The SUR of 13 2 -OH-BPME was recorded in mice bearing Lewis lung carcinoma after i.v administration of 7.8 αmole/kg body weight at different incubation time intervals. The photosensitizer was chemically extracted from selected tissues and concentrations were measured by absorption spectroscopy. The parenchymatous organs liver, spleen, and kidney as well as the lung showed maximum 13 2 -OH-BPME uptake ratios of 1.5 up 5.4 between 2 h and 4 h incubation times. The malignant tissue showed high 13 2 -OHBPME SUR between 2 h and 12 h post injection with a maximum SUR of 1.2 at 8 h incubation time. The 13 2 -OH-BPME SUR in muscle tissue, which represented the normal tumour surrounding tissue, and in the skin were very low and never exceeded 0.09 and 0.3 in muscle and skin, respectively. These results suggest that PDT using 13 2 -OH-BPME could be effective at a photosensitizer incubation time of about 8 h post injection, when the tumour 13 2 -OH-BPME SUR is maximum value, while muscle and skin exhibit minimum 13 2 -OH-BPME uptake. Therefore, phototoxic side effects on normal tissues in the tumour surrondings should not be induced.