Differential radioprotection of bone marrow and tumour cells by zinc aspartate

The radioprotector zinc aspartate did not inhibit the radiotherapeutic effect of gamma rays on human tumours grown as xenografts in immunosuppressed mice, while aminothiol radioprotectors afforded a slight inhibition. On the other hand, zinc aspartate significantly reduced the fall in the haematocrit and numbers of thrombocytes, erythrocytes and leucocytes caused by irradiation, indicating a sparing effect on bone marrow precursors of peripheral blood cells. This differential protection of neoplastic and normal cells may be of considerable benefit in clinical cancer radiotherapy, provided that zinc aspartate is better tolerated and has a more favourable therapeutic index in humans than aminothiol radioprotectors.