The Study Of Rats Rectums Damage After Using A Single Large-dose Radiatio And Oxaliplatin

Objective: To investigate the short term impact of Oxaliplatin combined with a single large-dose of radiation on rectum damage in rats, in order to provide a reference for its clinical application.Methods: 120 rats without any significant difference in weight were assigned randomly into 4 groups: A group:chemotherapy alone(intra-peritoneal injection of Oxaliplatin at 15mg/kg);B group: radiotherapy alone(6MV X ray 12 Gy, single dose radiation at rat pelvic);C group:concurrent chemo-radiotherapy(intra-peritoneal injection of Oxaliplatin at 15mg/kg, followed by 6MV Xray 12 Gy single dose radiation at rat pelvic). D group:control(abdominal injection of equivalent amount of saline);with 30 rats/group. The rats from different groups were sacrificed by anesthesia after being irradiated for 3,7,14,28,42 days, with 6 rats/time point. Morphological changes were observed by HE staining. Immunohistochemical streptavidin-peroxidase(S-P) method was used to quantify Bcl-2 and Bax protein expression in the rectum tissue.Results: Group C rats had the most severe rectum goblet cell reduction, random alignment of withered glands, as well as presence of a large quantity of inflammatory cells and occurrence of fibrosis. The similar reactions could also be seen in group A and B,but the degree was lighter. Expressions of Bax were significantly different between each experimental group and each time point( FBax=25.151~40.396,P<0.01).The expression of Bax in each experimental group was higher than that in the group D on day 3and7(F=178.016~185.543,P<0.01), and the highest was the group C on day 7(p<0.01). The expression of Bax in each experimental group on day 14,21,42 was lower than that in on day 3and7, with statistical significanc(F=174.152~195.069,P<0.01).The positive expression rate of Bcl-2 significantly different between each experimental group and each time(F=10.644~66.889,p<0.01). The expression of Bcl-2 in each experimental group on day 7 was lower than other each point in other time(F=418.076,P<0.01), and the lowest was the group C on day 7(p<0.01). With the extension of time, the expression rate gradually uplifted. With statistical significanc higher than the control group(F=428.861~606.655,P<0.001),with statistical significance. Then with the extension of time, the positive expression rate gradually uplifted in group C. The expression of Bcl-2 in group C on day 14,21,42 was higher than that in on day 7, with statistical significanc(F=428.861~513.760,P<0.01).Conclusion: Compare with chemotherapy and radiotherapy, concurrent chemo-radiotherapy may cause serious damage to rat rectum. The mechanism could involve increased Bax and decreased Bcl-2 protein expression and therefore the apoptosis of the cells. With increase in time, it was observed that Bax expression decreased, while Bcl-2 expression increased.