EFFECT OF PROLACTIN ON THE TADPOLE TAIL FIN. V. STIMULATORY EFFECT OF PROLACTIN ON THE INCORPORATION OF

DNA content of the tadpole tail fin was increased appreciably by the treatment of animals with bovine prolactin. Incorporation of 3 H-thymidine into DNA in the hormone-treated tail fins was remarkably stimulated as compared to the control ones. From the experiment on the effect of prolactin on the DNase activity, it is concluded that prolactin not only stimulates the synthetic parthway, but also suppresses significantly the catabolic one of the DNA metabolism.