Effects of prolactin, growth hormone, and triiodothyronine on prolactin receptors in larval and adult tiger salamanders (Ambystoma tigrinum).
The effects of porcine growth hormone (pGH) or ovine prolactin (oPRL) alone and in combination with triiodothyronine (T3) on renal PRL receptors were determined in both pre- and post-metamorphic tiger salamanders (Ambystoma tigrinum). The protein hormones were given at a dose of 1.0 micrograms/gm body weight/day and the T3 was given at 10.0 ng/gm body weight/day. The duration of treatment was 7 days. Effects on growth, and plasma thyroid hormone levels were also determined. Ovine PRL increased growth in both larvae and adults and reversed metamorphic changes. Administration of T3 increased the plasma T3 concentration, as measured by radioimmunoassay, and when given alone caused weight loss at both stages. The GH decreased plasma T4 and increased plasma T3 concentrations, indicating that it caused an increase in T4 deiodination. In adults the renal PRL receptor affinity of 2.9 +/- 0.7 x 10(10) L/mol and capacity of 160 +/- 22 fmol/mg protein were higher than the corresponding values of 1.8 +/- 0.3 x 10(10) L/mol and 29.2 +/- 3.8 fmol/mg in larvae. In adults only, there is an additional low-affinity, high capacity PRL binding site. The oPRL treatment decreased the binding capacity of 33.2 +/- 1.2 and 5.9 +/- 4.9 fmol/mg in adults and larvae, respectively. By contrast, pGH increased the capacities to 249 +/- 18 and 62.1 +/- 6.8 fmol/mg in adults and larvae, respectively. Treatment with T3 alone doubled the oPRL binding capacity to 58.3 +/- 4.7 fmol/mg in larvae, but there was no effect in adults. In both developmental stages the effects of oPRL and pGH on the receptors were not changed by the simultaneous T3 treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
Bres
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Department of Integrative Biology, University of California, Berkeley 94720.
Nicoll
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D000557:Ambystoma; D000704:Analysis of Variance; D000818:Animals; D002417:Cattle; D013006:Growth Hormone / Q000502:physiology*; D007668:Kidney / Q000378:metabolism; D007814:Larva; D011388:Prolactin / Q000502:physiology*; D011981:Receptors, Prolactin / Q000378:metabolism*; D012756:Sheep; D014284:Triiodothyronine / Q000097:blood / Q000502:physiology*
D011981:Receptors, Prolactin; D014284:Triiodothyronine; D011388:Prolactin; D013006:Growth Hormone