Comparison between the oxygen removal rate and the histological structure of normal and tumour tissues

Blood flow and oxygen supply to human mammary carcinomas transplanted into nude rats

Blood flow of human mammary carcinomas heterotransplanted into immune- deficient rnu/rnu-rats is low. It decreases further with increasing tumor wet weight, the mean value being comparable to that of mammary carcinomas in patients. The O2 consumption rate of the heterotransplanted tumors decreases with increasing tumor wet weight and again is comparable to that of mammary carcinomas in patients. Furthermore, it is directly proportional to the O2 availability which in turn is mainly determined by TBF. The O2 utilization of the human mammary carcinomas heterotransplanted into nude rats is already high in small tumors and increases only slightly with increasing tumor weight. From these results and taking into account an impairment of convective and diffusive O2 transport it can be concluded that the O2 consumption rate of the tumor cells is mostly determined by the the O2 supply and not by the actual demand of the cancer cells. This finding holds true for different tumor cell lines in different species.

The accuracy and spatial resolution of the measurement of tissue oxygen removal rate

An analysis is presented of factors determining the accuracy and spatial resolution of a method for the estimation of oxygen removal rate in tissues using a multi-cathode electrode placed on the tissue surface. The effect of oxygen consumption by the cathodes is shown to be small for 25-micrometer diameter cathodes, but covering the tissue surface with a thin oxygen oxygen-permeable plastic film can introduce a systematic error into the estimate of removal rate, the size of which depends upon the oxygen diffusion coefficient and solubility in the plastic compared with those in the tissue. Spatial resolution is shown to be adequate for distinguishing changes in removal rate over distances of a few hundred microns, and the averaging of removal rate in the direction normal to the tissue surface is weighted heavily towards the superficial tissue layer.