The fate of hematoporphyrin derivative (HpD, 10 mg/kg) was studied with microspectrofluorimetry in frozen tissue slices from female rats. In infact animals we observed the maximal incorporation of HpD in the small intestine mucosa, liver, lung, stomach and blad-der in 30 minutes, and in the skin and kidney - in 6 hours after an intravenous injection. In cancerous organism HpD was usually retained for 6-12 hours in different organs and for 12-48 hours in the tumor. Thanks to this the tumor/organs ratio achieved 2-150 times for tissue concentration and 2-11 times for fluorescent-contrast by the 6th hour after intravenous injection. Thus, the optimal time for experimental studies of carcinosarcoma photodynamic therapy with laser irradiation was found to be 4-6 days after its transplantation and 6-12 hours after intravenous HpD administration.
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