Radioprotective effect of mexamine and cystamine on animals exposed to hypokinesia and ionizing radiation

Experiments were done on male white rats. The experimental animals were placed, for 5, 15, 30, and 60 days, in cages that limited their mobiltiy. The control rats were allowed normal activity. Standard rations were fed. The controls and the experimental animals were subjected to total-body irradiation from Co-60 in a single 800-R dose. Mexamine (5-methoxytriptamine hydrochloride) at 20mg/kg and cystamine at 75mg/kg (doses of the substances considered basic) were used as radioactivity protectants. The substances were administered intraperitoneally 10 to 15 min. before irradiation. Controls were given 0.9% NaCl solution. The 30-day survival and the average prolongation of life of the animals that died were determined. The protective effect of mexamine and cystamine in rats living in a normal mobility regime was 63-83.7% in one group and 65.1-72.5% in another. Limited mobility for 5-15 days did not increase the protective effect of the radio-protective substances used, but in animals further limited in activity (30 and 60 days) there was a sharp decrease: In the 30-day hypokinetic conditions the protective effect of mexamine was decreased 2.5-fold, and the cystamine, 2.2-fold. In the 60-day hypokinetic conditions the pretective action of mexamine was decreased 3.5-fold and cystamine, 3.6-fold. The average prolongation of life of the experimental animals decreased starting with 15 days of preliminary limitation of the mobile activity (E.F.)