[The simultaneous measurements of time-dependent laser-induced fluorescence intensity of hematoporphyrin monomethyl ether in animal tissues with rheumatoid arthritis].

ABSTRACT

Since the selectivity of photodynamic therapy (PDT) depends on the distribution of a photosensitizer in a tissue during the treatment, an investigation of drug distribution is a key step for performing PDT effectively. The distribution of photosensitizer absorbed in tissues is adjusted by the animal body system, so an apparatus that can measure the fluorescence intensity of photosensitizer in different tissues of the same body simultaneously is in demand. To achieve precise estimate of tissue selectivity of the photosensitizer, a spatially separated three-channel laser-induced fluorescence (LIF) detection system was set up and employed in the present study to measure the fluorescence intensity of Hematoporphyrin Monomethyl Ether (HMME) in different tissues of the same body simultaneously. The time-dependent variations in the concentrations of HMME within the skin,cartilage, normal synovium and inflammatory synovium of rabbit were monitored in vivo. The results obtained showed that the synovium has higher absorptivity of HMME thanthe skin and cartilage. The difference is distinct from the very beginning of injection. Although the quantity of HMME absorbed in the inflammatory synovium is not very high in the first 20 min, it is still 6 times higher than that in the skin and cartilage. In addition, the absorptivity of HMME is much stronger for the inflammatory synovium than that for the normal synovium. If thelaser beam irradiates outside the joint for the rheumatoid arthritis, tissues around the inflammatory synovium have less HMME, thereby causing weak PDT effect. This would help reduce the side effect of PDT. Thus we suggest that for PDT treated rheumatoid arthritis, taking the first 20 min after the injection for outside-the-joint excitation employing HMME maybe a good choice.