title: Characterization of renal prolactin-binding sites of two amphibians (Ambystoma tigrinum and Rana catesbeiana) and a reptile (Pseudemys scripta elegans).
abstract: The specific binding of 125I-ovine prolactin (oPRL) to renal membrane preparations from Pseudemys scripta elegans, Ambystoma tigrinum, and Rana catesbeiana was characterized. All three membranes showed specific oPRL binding that was dependent upon time, temperature, pH, and membrane concentration. Scatchard analysis of the binding of 125I-oPRL revealed high-affinity sites with KA values of 2.1 X 10(10), 3.6 X 10(10), and 1.25 X 10(10) M-1 for kidney membranes of Pseudemys, Ambystoma, and Rana, respectively. In addition, there was a low-affinity site on the Ambystoma membranes. The binding capacities ranged from 31 to 70 fmol/mg of membrane protein. The hormonal specificity of these membranes was studied by competing increasing amounts of oPRL, human growth hormone (hGH) derived from recombinant DNA techniques, bovine (b) GH, and human placental lactogen (hPL) with 125I-oPRL. The oPRL standard and hGH were the most potent competitors in all three assays, although hGH was not as potent as the oPRL. Human PL was moderately active in the turtle kidney assay, weakly active in the Ambystoma radioreceptor assay, and inactive in the bullfrog assay. Bovine GH had low potency on the turtle membranes and was inactive in the amphibian assays. The results of these studies indicate that the characteristics of renal PRL receptors of Pseudemys, Ambystoma, and Rana are similar to those of lactogenic receptors throughout the vertebrates. In addition, these data provide evidence for the first time of renal PRL receptors in a reptile.
mesh_terms: D000557:Ambystoma; D000818:Animals; D001665:Binding Sites; D005260:Female; D007668:Kidney / Q000378:metabolism*; D008297:Male; D011388:Prolactin / Q000378:metabolism*; D011892:Rana catesbeiana; D011981:Receptors, Prolactin / Q000378:metabolism*; D013045:Species Specificity; D014426:Turtles
chemical_list: D011981:Receptors, Prolactin; D011388:Prolactin