Reticuloendothelial activity during the growth of rat sarcomas.

SUMMARY The clearance of colloidal carbon from the blood stream of rats bearing methylcholanthrene-induced sarcomas has been studied. Growth of both primary and isotransplanted tumors greatly enhances the clearance of carbon. This effect is greater with increasing tumor size. The uptake of radioactive colloidal gold has been studied following intravenous injection. The final distribution of colloid is not altered by tumor growth. The use of colloid gives a quantitative measure of reticuloendothelial activity, that reflects macroscopic and microscopic changes occurring in the spleens of rats bearing methylcholanthrene-induced sarcomas.