Changes in carboxypeptidase A, dipeptidase and Na+/K+ ATPase activities in the intestine of rats orally exposed to different doses of cadmium.
The purpose of the present study was to evaluate the effect of cadmium on some protein digestive and absorption enzymes in rats. Thirty-six rats were grouped into three groups of 12 animals each; one group received deionised water and acted as control. One group received 445 microM Cd and the last group received 890 microM Cd in their drinking water for a period of one month. The results obtained indicate that increasing the level of cadmium from 445 microM to 890 microM in the drinking water of the rats led to 29% and 23% increase in accumulated cadmium in the proximal and distal small intestine respectively. The body weight gain of rats exposed to 445 microM and 890 microM Cd was decreased by about 24% and 43% respectively when compared with the control. The activities of carboxypeptidase A, dipeptidase and Na+/K+ ATPase were reduced in the mucosa of the proximal end of the small intestine of cadmium exposed rats. The reduction was dose dependent; with the 890 microM Cd exposed rats displaying the least activities. In the distal small intestine, the activities of these enzymes were restored in the 445 microM Cd exposed rats to levels that were not statistically different (P > 0.05) from those observed in the controls. In the 890 microM Cd exposed rats, dipeptidase activity improved by about 80% compared with the activity of the enzyme in the proximal small intestine. Likewise, Na+/K+ ATPase activity increased by about 125% compared with the observed level in the proximal small intestine. The study suggests that cadmium given to rats in drinking water compromise protein digestion and absorption of nutrients particularly in the proximal region of small intestine and could account for weight reduction associated with cadmium toxicity.