Epicardial Hemprotein Oxygenation and Redox State Through Spectral Curve Fitting

Clyde H. Barlow, Emily J. Bailey, Brian J. Mundy, David S. Pratt, Jr., William C. Sloan, Katherine A. Kelly, and Jeffrey J. Kelly

The Evergreen State College, Olympia, WA 98505
Barlow Scientific, Inc., Olympia, WA 98502

C.H. Barlow, E.J. Bailey, B.J. Mundy, D.S. Pratt, Jr., W.C. Sloan, K.A. Kelly and J.J. Kelly  (1993)  Epicardial hemprotein oxygenation and redox state through spectral curve fitting.  FASEB J.  7: A1074.  Real time measurement of mitochondrial redox states and hemoglobin (Hb) and myoglobin (Mb) oxygen saturation in tissues is desirable to monitor tissue responses to oxygen delivery and demand. We have developed an optical method for the simultaneous determination of cytochrome reduction and Hb and Mb saturation in vivo. Visible reflectance spectra were recorded from epicardial surfaces during heart perfusion using a fiber optic probe and 1024-element diode array spectrometer. Rat hearts were retrograde perfused with O2 saturated HEPES buffer containing sheep erythrocytes Hct = 5% at 37 C. Hearts were studied under conditions of hypoxia, ischemia, cyanide inhibition and variable hematocrit to resolve spectral signatures of reduced cytochromes, MbO2, Mb, HbO2 and Hb. Effects from tissue scattering of light were included in the spectral basis set. Concentrations of the five species Hb, HbO2, Mb, MbO2 and reduced cytochromes were determined by curve fitting reflectance spectra using matrix inversion. Saturation curves generated from these analyses reveal effects of oxygen gradients under differing tissue and oxygen supply conditions. The method is reasonably robust and transferable among hearts.

This research was supported by NIH grants HL43473 and HL47924.

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