Differential radioprotection of tissues in C3H/J mice by a combination of 5-hydroxy L-tryptophan with 2-aminoethylisothiuronium bromide hydrobromide.

Differential radioprotection between normal tissues and carcinoma was observed in C3H/J mice treated with a combination of 5-hydroxy L-tryptophan (5-HTP, 100 mg/kg) and 2-aminoethylisothiuronium bromide hydrobromide (AET, 20 mg/kg). Protection to normal tissues was judged by LD50(30) and by radiation induced damage to bone marrow(BM) using clonogenic ability of blood forming stem cells (10 day CFUs) as the criteria. Pretreatment with 5-HTP + AET combination 30 min before whole body gamma radiation (WBGR) enhanced the recoveries of the number of blood forming stem cells in BM of irradiated mice after 0, 7th and 10th day of irradiation. LD50(30) for C3H/J mice was 7.3 Gy and the dose modifying factor (DMF) of 5-HTP + AET combination was 1.76. On the contrary, pretreatment with this combination did not protect the mammary carcinoma transplanted in C3H/J mice, when exposed to 80 Gy soft X-rays.