Effects of prolactin and growth hormone on growth and metamorphosis of tadpoles of the frog, Rana pipiens

Mammalian prolactin at doses of 1-50 [mu]g/day promoted growth (increased wet weight, dry weight and body length) in Rana pipiens tadpoles. Mammalian growth hormone (GH) promoted growth only at the higher doses (50 [mu]g/day and above) and was not so effective as prolactin.Prolactin also inhibited metamorphosis (at doses of 5 [mu]g/day and above). Inhibition of metamorphosis did not appear to be due to reduction in tissue sensitivity to thyroxine since prolactin-treated tadpoles metamorphosed in response to exogenously administered thyroxine (4-100 [mu]g/liter) to the same extent as controls. Prolactin promoted further growth in tadpoles in which the thyroid level had been reduced with thiouracil or by thyroidectomy. This indicates that growth promotion caused by prolactin is not just the result of thyroid inhibition, although it is possible that a portion of the growth stimulation is due to the antithyroid action of prolactin.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32919/1/0000301.pd

Effects of hypophysectomy, prolactin, and growth hormone on growth of postmetamorphic frogs

Hypophysectomy of juvenile postmetamorphic frogs (Rana pipiens) reduced growth (wet weight and length) compared to sham hypophysectomized controls. Mammalian growth hormone at doses of 10-50 [mu]g/day promoted growth in intact frogs during a 2-month period. However, 5 [mu]g/day of GH for 1 month did not promote growth. Mammalian prolactin did not promote growth in postmetamorphic frogs over a 2-month period at doses between 5 and 50 [mu]g/day.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32921/1/0000303.pd

Effects of hypophysectomy and thyroidectomy on salt balance in the plethodontid salamanders, Desmognathus fuscus and Desmognathus monticola

Hypophysectomy significantly reduced serum sodium levels in Desmognathus fuscus and D. monticola . Prolactin, corticosterone or aldosterone replacement failed to restore serum sodium to control levels. Hypophysectomy also led to decreases in in vitro integumental potential difference and shortcircuit current, which were not restored to control levels by prolactin or corticosterone. Thyroidectomy significantly reduced the level of serum sodium in D. monticola , but it increased in vitro potential difference and short-circuit current. Thyroxine treatment of either hypophysectomized or thyroidectomized D. monticola completely restored serum sodium, potential difference and short-circuite current to control levels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47122/1/360_2004_Article_BF00799050.pd

Effects of prolactin and somatotropin on growth and metamorphosis of amphibians

Mammalian prolactin stimulates growth and inhibits metamorphosis of larvae of several species of amphibians. Mammalian somatotropin has little or no effect upon larval growth or metamorphosis unless used in high concentrations. The evidence behind these statements and some of the implications are critically evaluated. Growth of postmetamorphic amphibians is stimulated by somatotropin but not by prolactin. The possible biological significance of this apparent transition from prolactin to somatotropin regulation of growth in the pre- and postmetamorphic stages of development is discussed in terms of possible mechanisms involved in the transition, and in terms of the adaptive significance of the change.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34198/1/0000487.pd

Growth Responses Of Larval And Postmetamorphic Rana Pipiens To Prolactin And Growth Hormone.

PhDZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/187916/2/6902294.pd