EFFECT OF PROLACTIN ON THE TADPOLE TAIL FIN. III. EFFECT OF PROLACTIN ON THE HYDROXYLATION OF PROTOCOLLAGEN-PROLINE...

The fact that bovine prolactin stimulates the collagen synthesis of the tadpole tail fin was confirmed by the present experiments, in which specific radioactivity of 14 C-hydroxyproline hydroxylated from the incorporated 14 C-proline was measured by the method different from that of the previous report (Yoshizato and Yasumasu, 1970). Stimulatory effect of prolactin on the incorporation of 14 C-proline into the collagen fraction did not disappear even under the conditions, where the activity of protocollagen-proline hydroxylase was inhibited by α,α'-dipyridyl. In fact prolactin had not a significant effect on the activity of the emzyme. It, therefore, is concluded that the hormone promotes the incorporation of 14 C-proline into collagen without affecting the hydroxylation step of the protein synthesis.