Thyroxine induced tail resorption in vitro as affected by anterior pituitary hormones.

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AbstractIt has been previously shown that discs prepared from the tail fins of tadpoles, (R. pipiens), survive in vitro for several weeks and respond to thyroxine by undergoing resorption. Discs cut from animals during metamorphic climax, demonstrate rapid resorption without addition of exogenous thyroxine.Discs were cut from tadpoles in early prometamorphosis and in climax and were implanted with either whole pituitary glands or the separate lobes. Controls were either implanted with cerebrum or sham‐operated. These discs were maintained in solutions of thyroxine in Hanks medium, (3 ppb or 6 ppb), or in control, Hanks medium. In addition, discs from animals in early prometamorphosis were injected with either prolactin, GH, or control medium and discs from animals at climax were immersed in solutions of prolactin, GH, FSH and control medium.The results of these experiments demonstrates that the anterior pituitary, of the tadpole releases a factor that interferes with the action of thyroxine on tail discs in vitro. Prolactin and GH demonstrate similar activity but are less effective than the graft pituitaries. The results are interpreted to indicate that antagonism exists with respect to tail resorption between a pituitary growth factor, (possibly a prolactin‐like, or GH‐like molecule) and thyroid hormone.