Prolactin is not a juvenile hormone in Xenopus laevis metamorphosis

摘要

Prolactin (PRL) is widely considered to be the juvenile hormone of anuran tadpoles and to counteract the effects of thyroid hormone (TH), the hormone that controls amphibian metamorphosis. This putative function was concluded mainly from experiments in which mammalian PRL was injected into tadpoles or added to cultured tadpole tissues. In this study, we show that overexpres- sion of ovine or Xenopus laevis PRL in transgenic X laevis does not Prolong tadpole life, establishing that PRL does not play a role in the life cycle of amphibians that is equivalent to that of juvenile hormone in insect metamorphosis. However. overexpression of IRL produces tailed frogs by reversing specifically some but not all of the programs of tail resorption and stimulating growth of fibroblasts in the tail. Whereas TH induces muscle resorption in tails of these transgenics, the tail fibroblasts continue to proliferate resulting in a fibrotic tail that is resistant to TH.