Growth-promoting and antimetamorphic hormone in pituitary glands of bullfrogs

Among the fractions separated from pituitary glands of both larval and adult Rana catesbeiana by disc gel electrophoresis, only a fast moving protein fraction had both a pronounced stimulating effect on the collagen synthesis in the tail fin of bullfrog tadpoles and a suppressive effect on T₄-induced resorption of Bufo bufo japonicus tadpole tails in vitro. Pigeon crop-sac test revealed that the fraction had a pronounced prolactin activity. It was demonstrated that this fraction was about four times as potent as bovine prolactin in promoting collagen synthesis in the tadpole tail fin.