Accumulation of labelled vitamin B12 in some transplanted tumours

The accumulation of labelled vitamin B12 in four different kinds of transplanted tumour was studied using whole‐body autoradiography and impulse counting. The tumours were 90Sr‐induced soft fibroblastic osteosarcomas, spontaneous mammary carcinomas, Ehrlich ascites and Moloney virus‐induced tumours. The 90Sr‐induced soft sarcoma, which was the most rapidly growing tumour, showed the greatest uptake of radio‐B12, the concentration being higher than in any normal tissue. In all tumours the radioactivity was localized to the peripheral, still actively growing parts. It is suggested that a connection exists between growth rate and accumulation of B12 and that B12 is needed for rapid cell multiplication.