FLUORESCENT CHARACTERISTICS AND PHARMACOKINETIC PROFILES OF THE FLUORESCENT-PROBE BCECF IN VARIOUS TISSUES - THE ROLE OF BLOOD CONTENT

The purpose of this study was to investigate the in vitro and in vivo spectral characteristics of the fluorescent pH-sensitive probe bis-car boxyethylcarboxyfluorescein (BCECF) in different tissues and its fluor escence kinetics profiles. The in vivo study was performed on anesthet ized adult Wistar rats, After intravenous administration (4.8 mg/kg), fluorescence spectra were recorded on the following tissues: skin, an isolated blood vessel and liver, Measurements performed in vitro on bl ood samples show modifications of the BCECF emission spectrum with a b lue-shift (10 nm) and a low fluorescence emission, Blood content great ly influences the pH measurement by increasing the I(490 exc., 530 em. )/I(470 exc., 530 em.) fluorescence ratio value (ratio of the fluoresc ence intensities at 530 mn following excitation at 470 mm and 490 nm) when the hematocrit is high, A 0.35 ratio difference is observed betwe en a BCECP-buffered solution and blood samples of 44% hematocrit. The emission spectra recorded on the skin are quite similar to the emissio n spectrum of BCECF in aqueous solution and are consistent with an ext ravascular localization of the dye a few minutes after injection, On t he contrary, spectra recorded on the blood vessel and the liver are mo re similar than those recorded in vitro on high hematocrit solutions, Kinetic profiles in skin, liver and isolated blood vessels compared to the clearance obtained by blood sampling pro,ide information about ti ssue perfusion, Then the variation of in vive spectra in different tis sues may be taken into account to measure tissue pH with special regar d to the blood content of the illuminated area and the time range in w hich the measurement is performed.