Ultrastructural changes in rat colon following 1,2-dimethylhydrazine-induced colon carcinogenesis: protection by zinc.

The present study evaluated the modulatory effects of zinc on 1,2-dimethylhydrazine (DMH)-induced ultrastructural changes in rat colon as well as on [(3)H]thymidine uptake and [(14)C]D-glucose metabolism. The rats were segregated into four groups: normal control, DMH treated, zinc treated, DMH + zinc treated. Initiation and induction of colon carcinogenesis was achieved through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 and 16 weeks, respectively. Zinc was supplemented to rats at a dose level of 227 mg/L in drinking water, ad libitum for two different time durations of 8 and 16 weeks. The study revealed a significant decrease in zinc concentration in serum and colon following DMH treatment to rats, which upon zinc supplementation were recovered to near normal levels. A significant increase in in vitro [(3)H]thymidine uptake was observed following 16 weeks of DMH treatment. Further, a significant increase in the [(14)C]glucose turnover was observed following 8 and 16 weeks of DMH treatment. Simultaneous supplementation of zinc to DMH-treated rats for 16 weeks significantly decreased the uptake of [(3)H]thymidine and [(4)C]glucose when compared to DMH alone-treated rats. Changes in the ultrastructural architecture of colonic cells were evident following both treatment schedules of DMH; however, the changes were more distinguishable following 16 weeks of DMH treatment. The most obvious changes were seen in nuclear shape and disruption of cellular integrity, which upon zinc supplementation was appreciably improved. In conclusion, the study suggests positive beneficial effect of zinc against chemically induced colonic preneoplastic progression in rats.