The use of fluorescent probes to identify regions of transient perfusion in murine tumors.

Sequential intravenous injection of two fluorescent stains, Hoechst 33342 and DiOC7(3), can be used to quantify transient perfusion in experimental tumors. Regions of unmatched staining, indicative of intermittent perfusion, occur when vessels open or close in the 20 minute interval between administration of the dyes. In the murine SCCVII carcinoma, 8.9 +/- 2.4% (SD) of vessels in 0.5 g subcutaneous tumors had labelling of adjacent cells with only one stain, suggesting complete vessel closure lasting at least 5 minutes. Regions of intermittent perfusion were not homogeneously distributed throughout the tumor and larger tumors exhibited more mismatch than smaller tumors. Transient perfusion was observed in both subcutaneous and intramuscular tumor implants and was not significantly affected by restraint of the animal or by ketamine/diazepam anesthesia.