The effect of prolactin and thyroxine on tail resorption in R. pipiens: in vivo and in vitro.

Thyroxine induces tail resorption in anurans both in vivo and in vitro. This event is accompanied by an increase in the activity of the hydrolytic enzymes acid phosphtase and B-N-acetylglucosaminidase. Prolactin treatment promotes tail growth and directly antagonizes the action of thyroxine on tail tissues. This is evident at the gross morphological level as well as at the biochemical level where prolactin inhibits the increase in activity on the hydrolytic enzymes that occurs during thyroid hormone induced resorption.