[en] It has been studied whether there is a correlation of the radioprotective effect of cystamine (50 and 150 mg/kg by base) and its analogue, N',N'-tetramethyl cystamine (130 mg/kg by base), with the ability of these compounds to rise the endogenous serotonin content of radiosensitive organs 20 and 60 minutes after intraperitoneal administration to mice. The ability of sulphur-containing radioprotectors does not necessarily correlate with their preventive properties: an ineffective radioprotector analogue, N',N'-tetramethyl cystamine, has the same effect on the endogeneous serotonin level as the protector itself