Radioprotective Effect of ε-Aminocaproic Acid in Acute Total-Body Gamma Irradiation in Rats.

BACKGROUND

Acute radiation injury to the small-intestinal mucosa and the hematopoietic system is a key determinant of early mortality after high-dose total-body irradiation. ε-Aminocaproic acid (EACA), a lysine analogue with antifibrinolytic properties, has been proposed as a potential radioprotective agent, but its effects on intestinal and hematologic injury remain insufficiently characterized.

METHODS

In this experimental study, 240 male Wistar rats were subjected to single-dose total-body γ-irradiation at 10.6 Gy and randomized into six groups: two non-irradiated controls (CG-1, CG-2), an irradiated control without treatment (CG-3), and three experimental groups receiving EACA (EG-1: 3 h before irradiation; EG-2: 3 h after irradiation; EG-3: both 3 h before and 3 h after irradiation). Pain behavior was assessed using the Rat Grimace Scale. Intestinal damage was evaluated by a modified Radiation Injury Intestinal Mucosal Damage Score (RIIMS_sum), villus and crypt morphometry, and qualitative histology of the ileum. Hemoglobin, leukocytes, and platelets were measured serially, and 30-day survival was analyzed using Kaplan-Meier curves with log-rank tests.

RESULTS

Across all EACA regimens, the odds of being in a higher Rat Grimace Scale pain category were reduced compared with CG-3, with the strongest effect in EG-3 (OR 0.42; 95% CI 0.31-0.58). At 72 h after irradiation, the cumulative RIIMS score was lower in EACA-treated groups by approximately 17-36% versus CG-3, with the lowest injury in EG-3 (18.5 vs. 29.0 points). EACA attenuated shortening and blunting of villi, preserved crypt architecture, and mitigated anemia, leukopenia, and thrombocytopenia. Thirty-day survival was 20% in CG-3 and 60%, 65%, and 80% in EG-1, EG-2, and EG-3, respectively (all p < 0.05 vs. CG-3).

CONCLUSIONS

ε-Aminocaproic acid exerts a pronounced, timing-dependent radioprotective effect in a rat model of acute total-body γ-irradiation, concurrently reducing the severity of radiation enteritis, hematologic toxicity, and early mortality. These findings support further investigation of EACA as a candidate adjunct in the prevention of acute radiation injury.