Radio-protective dosimetry of Pangasius sutchi as a biomarker, against gamma radiation dosages perceived by genotoxic assays

Exposure to ionizing radiation is harmful to any living organism. It may cause varying levels of genetic mutation or ultimately death. Synthetic compounds have been used to counteract the hazardous effect of radiation on the live cells, but the possibility of these synthetic compounds being harmful to the organism being treated also exists. Herbal formulations are thus being explored as a possible alternative for the synthetic radioprotectant. Induction of DNA damage in fishes caused by ionizing radiation and its protection by phytocompounds is a hardly studied topic. In this study, we analyzed the radioprotective effect of Gymnema sylvestre leaves extract (GS) and its active compound gymnemagenin (GG) against different doses of gamma radiation (Co-60) on the freshwater fish Pangasius sutchi. The radioprotective efficacy was assessed by micronuclei and alkaline comet assays. The freshwater fish P. sutchi was pre-treated with intramuscular injection (IM) of amifostine (83.3 mg/kg of BM.), GS (25 mg/kg of B.W.) and GG (0.3 mg/kg of BM.), 1 h prior to the gamma radiation. The fishes were exposed to LD30, LD50 and LD70 of gamma radiation and the protection activities were assessed by analyzing the number of micronuclei (MN) and erythrocytic abnormalities in the blood after 2, 4, 8, 16 and 32 days after exposure. Compared to the irradiated fishes, frequency of erythrocytic abnormalities were decreased in response to the radio-protection in the amifostine treated groups for all three doses of gamma radiation (LD70-77.62%), (LD55-80.11%) and (LD30-82.30%); GS (LD70-62.66%), (LD50-69.74%) and (LD30-70.81%); and GG (LD70- 49.42%), (LD50-53.43%) and (LD30-58.42%). Similarly, a significant radio-protective effect in terms of decremented DNA damage was observed using the comet assay after post exposure. The percentage of protection noted for amifostine was (LD70-58.68%), (LD50-64.52%) and (LD30-74.40%); GS (LD70-53.84%), (LD50-59.02%) and (LD30-65.97%); GG (LD70-49.85%), (LD50-52.56%) and (LD30-64.30%). From the current study, we can conclude that the radioprotective efficacy of the GS is similar to the synthetic compound (amifostine) and also greater than the bioactive compound (GG). The synergetic effect of the plant extract which leads to a better protection than the bioactive compound must be further studied. MN and Comet assays can easily identify the damage due to radiation exposure and thus can be used as predictive biomarkers for aquatic organisms exposed to radiation.