Various medications affect the systemic circulation and organ oxygenation causing dilatation or constriction of blood vessels. Imminent liver failure can be generated by reduced perfusion of different origins. In this case hepatic vasodilatation would be a therapeutical approach for improving patient's condition. Our examinations have been performed in perfused rat liver using spectrometric methods. Two defined areas of the liver were measured punctually. We compared the influence of Tetramethylpyrazine and Glyceroltrinitrate on hemoglobin oxygenation (HbO 2 ) and concentration (Hb-conc.) in rat liver after application of Norepinephrine, which caused a mid decrease in hemoglobin oxygenation of 47,9 %. Both increased the HbO 2 , but differed from each other in manner of time and extent. Tetramethylpyrazine indicated a longer effect than Glyceroltrinitrate. Futhermore, HbO 2 and Hb-conc. showed a conversed relation. From the shape of the absorption spectra it is possible to derive the oxygenation of hemoglobin.
Subcellular particles (mitochondria, cellular pigments etc.) are mainly responsible for light scattering in living tissues in relation to the functional state. 2-D images clarify the respective tissue status during normoxia or anoxia such as the redox state of cytochromes. We realized tissue imaging of twelve isolated perfused rat livers stained with Merocyanine-540 during normoxia, hypoxia and anoxia. Merocyanine-spectra have shown a maximum fluorescence peak at 596 ± 2 nm. The optical response increased under desoxygenation and decreased under reoxygenation and might be correlated to electrical potential alterations. Furthermore, we record oscillations with frequencies over 7/sec (420/min) which might be correlated to intracellular processes. The additional use of dyes for tissue imaging gives us the opportunity of new insights into organ function.
Spectrometry is a well established method for in vitro and in vivo measurements. For interpretation of experimental results and patient monitoring it is important to regard the catchment volume and penetration depth of backscattered light. We investigated different suspensions of rat liver mitochondria as well as rat liver homogenate in a scattering chamber combined with a scanning procedure. To compare these results with a common used medium we measured Lipofundin® 2% additionately. The highest light intensity caused Lipofundin® 2%, followed by 100% mitochondrial concentration, liver homogenate and 50% mitochondrial concentration. Most of times the light penetrates slightly pronounced in lateral than in forward direction. Furthermore, we investigated the dependence of optical fibers with different diameter on catchment volume and penetration depth. Optical fibers were applied with a diameter of 200 µ m and 250 µ m respectively presenting a great increase in catchment volume and penetration depth in the larger one.
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