Protective Effect of Carica papaya   Fruit Extract Against Gamma Radiation-Induced Oxidative Damage in Postnatal Developing Rat Cerebellum

Radiation side effects have been reported to induce oxidative stress by free radical generation. The protective effect of Carica papaya (CP) fruit extract, vitamins C and E against gamma radiation-induced oxidative damage on postnatal developing rat cerebellum was studied. Forty-two female Wistar rats were mated and divided into six groups (n=7). Group A served as control and received water, Group B received a dose of 2.5 Gy irradiation only, Group C received 200 mg/kg aqueous extract of CP only, Group D received 200 mg/kg aqueous extract of CP + 2.5 Gy irradiation, Group E received 500mg/kg Vitamin E + 2.5 Gy irradiation and Group F received 200 mg/kg Vitamin C + 2.5 Gy irradiation. The pregnant rats were exposed to irradiation with radiation from Cobalt 60 delivered by an AECL machine in prone position on 7th day of pregnancy, while aqueous extract of CP, Vitamin E and Vitamin C were administered orally from day 7 of gestation to postnatal day 28. Behavioural and haematological assessments of pups were done on day 21, and killed. Some cerebella of the pups of days 1, 7 14 21 and 28 were fixed in 10% formol-saline for histological and histomorphometric studies, while other cerebella of day 21 were preserved in phosphate buffered saline at 4oC and pH 7.4 for biochemical assays. Data were presented as Mean ± Standard Deviation and analysed using ANOVA at p < 0.05. Results showed in the irradiated rats, a significant reduction in body weight, increased brain weight, decreased time spent on the forelimb grip, decreased haemoglobin (Hb) concentration and increased lipid peroxidation (LPO) and H₂O₂ levels in the cerebellum compared with the control, CP, vitamins C and E rats at p<0.05. Histologically, there was persistent external granular layer (EGL) as well as reduction in molecular layer (ML) thickness in the irradiated group compared with the control and other treated groups on postnatal day 21. In conclusion, 2.5 Gy whole body irradiation of pregnant rats induced oxidative stress in the developing rat cerebellum. Treatment, with aqueous extract of CP reduced the damage caused by irradiation when compared with vitamins C and E.

Keywords
Oxidative stress; gamma- radiation; Carica papaya; developing cerebellum