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

Abstract

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.