Growth Inhibition in Amphibian Larvæ by 4-Amino Pteroyl Glutamic Acid (Aminopterin)

A NUMBER of workers have demonstrated the inhibition of growth in the rat and mouse 1,2 , bacteria 3–5 , and in the chick 6–8 by means of folic acid antagonists. Seeger et al. 5 have shown that 4-amino pteroyl glutamic acid is a powerful antagonist of folic acid by the Streptococcus fæcalis R. test, and its toxicity in mammals has been well established. Karnofsky et al. 7 demonstrated quite conclusively that 4-amino pteroyl glutamic acid, as an analogue of folic acid, has the ability to inhibit growth in the chick, and the question arose as to whether this reaction could be found in a cold-blooded vertebrate as well. In this preliminary report, the growth inhibition of amphibian larvæ by 4-amino pteroyl glutamic acid is indicated, particularly in the growth phases in the middle and late larvæ. Studies on inhibition in early development, effects on embryo-genesis, and possible reversal effects are to be presented elsewhere at a later date.