The effect of hypoxic and histotoxic hypoxia on contractility and blood flow of the langendorff guinea pig heart preparation.

Abstract

For these investigations, reliable quantitative measurements of tissue oxygen supply — shortly called “tissue oxygenation” — are of crucial importance. As tissue Po2 histograms have shown, the Po2 of inflowing or outflowing medium cannot be safely taken as quantitative measure of tissue oxygenation because of the inhomogeneities within the microcirculatory bed. However, measurements of Po2 histograms need too much time. The heart muscle has the advantage that it possesses an intracellular O2 binding pigment, the myoglobin, which together with the cytochranes can and has been used for measuring tissue oxygenation (see 1). The problem was to find a quantitative evaluation method. We could show that in the wavelength range between 500 and 630 nm the reflection spectra of the hemoglobin-free perfused guinea pig heart is determined by the α- and β- bands of myoglobin, cytochrome aa3 and cytochrome (b+c). Experimentally it is possible to produce spectra of (1) deoxygenated myoglobin and reduced cytochrcenes, (2) fully oxygenated myoglobin and oxidized cytochranes and (3) oxygenated myoglobin and reduced cytochranes. Using these spectra as basic spectra a linear multi-component analysis can be performed by which the O2 saturation of myoglobin and the redox states of cytochrome aa3 and (b+c) are calculated (1). The measurement of a large wavelength range is of advantage as compared to the two-wavelength method since (1) it does not rely any more on the existence of isosbestic points and (2) the fit between measured and recalculated spectra can be continuously used to test the validity of the evaluation method (see Figure 2).KeywordsReflection SpectrumTissue OxygenationHypoxic HypoxiaQuantitative Evaluation MethodInflowing MediumThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.