Detection and quantitative estimation of metalloporphyrins in vivo

Spectrofluorometry, radioisotope (RI) labelling and high performance liquid chromatography (HPLC) can be used to estimate photosensitizer concentrations. The biodistribution of porphyrins and metalloporphyrins containing the bifunctional chelating agent diethylenetriamine pentaacetic acid (DTPA) was examined in tumour-bearing mice by nitrogen-pulsed laser spectrofluorometry (PLS) and RI labelling. The biodistribution of metalloporphyrin amino acid derivatives containing alkoxyl groups was also examined by PLS and HPLC analysis using an acetone powder extraction method. Spectrofluorometry is useful for estimating the biodistribution of porphyrins in tumour, lung, kidney and serum, but not in liver. However, spectrofluorometry cannot be used to evaluate the concentration of certain metalloporphyrins such as manganese complexes. The concentrations of porphyrins in liver measured by PLS and two other methods showed remarkable differences. RI labelling and HPLC analysis are obviously tedious methods. Therefore it seems practical to screen for a number of compounds using the spectrofluorometric method (PLS). Subsequently, the porphyrins which give good results with PLS should be measured using RI labelling and HPLC.