Efficiency of Antibiotics in Supplementing the Growth Effect of Beta Carotene in Vitamin A-Depleted Rats. ∗

Summary

The capacity of some antibiotics to stimulate additional growth in rats receiving a sub-optimum intake of Vit. A (as beta carotene) has been determined. The additional growth response obtained under the conditions of these studies ranged from essentially no additional growth when sodium acrylate or streptomycin was used to a 44% increase when tetracycline HCl was incorporated into the Vit. A-deficient diet. While relationship of structure of the antibiotic to growth-stimulating capacity was not fully apparent, the tetracyclines as a group appeared to be the most effective in this respect. This may have been related to the specific level of antibiotic feeding in that the 1 g/kg level had been found previously to be optimum when chlortetracycline was fed. This may not have been true for other antibiotics. The mode of action of certain antibiotics in the economy of Vit. A and beta carotene metabolism is being studied.