Effects of tetracycline on the absorption of 65zinc in rats

The effects of tetracycline on the absorption of orally ingested 65Zn was studied on rats by whole body counting assay. 65Zn was given as a single dose to groups of rats, five in each, which were started on tetracycline. Tetracycline was given in daily doses of 25 mg, 50 mg, 100 mg, and 200 mg for 10 days. From the 6th day of the study, 65Zn retention when plotted against time in a semilog plot, approximated linearity. The net absorption of 65Zn in the various groups was determined by extrapolating to zero time the linear curve segment of individual retention curves. Except for the lowest tetracycline dosage, tetracycline significantly impaired 65Zn absorption. The elimination rate of retained 65Zn from the 6th day was significantly higher in the group receiving 200 mg tetracycline as compared with the control group.