[Kinetics of 57Co-cyanocobalamin distribution in the organs and tissues of mice with transplanted tumors].

The distribution of cobalamin coenzyme precursor, 57Co-cyanocobalamin (57Co-CN-Cbl), in normal animals and in mammary adenocarcinoma (AC 755) and La leukemia-bearing mice has been studied during the exponential phase of tumour growth. The total uptake of radioactivity in the normal target organs was different. AC 755 took up 57Co-CN-Cbl selectively in all the periods of observation. In the case of La leukemia the highest rate of 57Co-CN-Cbl uptake in the spleen was found before its maximal hyperplasia. The accumulation of radioactivity in tumours led to a significant decrease in the total labelled cobalamin levels of the liver and kidneys. Analysis of the obtained kinetic curves revealed a different ability of AC 755 and leukemia cells for utilizing the pool of the endogenous cobalamin.