CORRELATION BETWEEN THE LIGHT-SCATTERING AND THE MITOCHONDRIAL CONTENT OF NORMAL-TISSUES AND TRANSPLANTABLE RODENT TUMORS

The development of noninvasive optical studies necessitates an underst anding of the biological parameters which affect light propagation in soft tissues. In the present report, we have measured the optical prop erties of various normal (i.e., perfused liver, brain, skeletal muscle , white adipose tissue) and neoplastic rodent tissues (i.e., glioma, h epatoma, mammary adenocarcinoma) by using time-resolved spectroscopy. The contribution of the hemoglobin (+ myoglobin in the case of muscle) to the total light absorption at 780 nm has been determined. This con tribution varies from about 25% (brain, skeletal muscle) to about 100% (white adipose tissue, 13762A mammary adenocarcinoma, 9L glioma). The se results are explained by different blood volume fractions in the ti ssues and by the existence at 780 nm of other chromophores, such as th e mitochondrial cytochrome oxidase. Secondly, the dependence of the li ght scattering of the tissue on both the cell and the mitochondrial co ntent has been analyzed. The results indicate that there is no correla tion between the light scattering and the DNA content, measured as an indicator of the cell number in the tissue. The scattering coefficient is proportional to both the succinate dehydrogenase activity and the mitochondrial protein content of the tissue, which are indicators of t he mitochondria content of the tissue when based upon estimates of tis sue wet weight. (C) 1995 Academic Press, Inc.