Whole-body retention of 65Zn after single and daily oral administration in young and adult mice

The whole-body retention of 65Zn in the young and adult mice after single and daily oral administration was investigated. The retention values for 65Zn in young mice were significantly higher than those of the old ones. Since significant differences were noted in the presence or absence of the fast declining component of the retention curves and since the final slopes of 65Zn retention curves were similar among all the age groups, the higher retention of 65Zn in the 7- and 14-day-old mice was probably attributed to its near-complete absorption from the G. I. tract, while the 21-day-old and adult mice absorbed 45 and 12 percent of the administered dose, respectively. It is also noted that the 7-day-old mice contained significantly higher 65Zn in the pelt and lower 65Zn in pancreas, liver and G. I. tract than those of the adult mice. When 65Zn was administered orally everyday over a period of two weeks, the young animals retained 50 percent of the administered dose at the termination of administration, while the adult retained 8 percent. Again, its difference could be attributed to an efficient intestinal absorption of young animals.