title: Characterization of the parathyrin receptor in renal plasma membranes by labelled hormone and labelled antibody binding techniques.
abstract: The parathyrin receptor in renal cortex has been investigated by studying the binding of 125I-labelled parathyrin, or of unlabelled parathyrin detected with 125I-labelled antibodies, to a partially purified plasma membrane fraction. The kinetics of hormone uptake demonstrated a biphasic response in both systems at 22 degrees C but this phenomenon was not detectable at 37 degrees C. Specific displacement of lactoperoxidase labelled 125I-labelled parathyrin occurred with 8 ng unlabelled bovine parathyrin. The apparent affinity constant was 2.3-10(8) M(-1) and the apparent binding capacity of the membranes 1.25 pmol/mg protein. Using the labelled antibody technique the receptor showed maximal binding at pH 7.0-7.5. As little as 80 pg bovine parathyrin produced a significant increase in binding of labelled anti-bovine parathyrin antibody and saturation of binding sites was demonstrated at 2.5 pmol/mg protein. Oxidized hormone showed undetectable binding. Treatment of membranes with phospholipases A or D, or Trypsin greatly reduced subsequent hormone binding. Prior incubation of membranes with 1-34 synthetic parathyrin decreased the binding of intact hormone whereas gastrin, insulin and glucagon had no effect. Growth hormone and calcitonin slightly increased parathyrin binding.
mesh_terms: D000818:Animals; D000937:Antigen-Antibody Reactions; D001666:Binding Sites, Antibody; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D002645:Chickens; D007672:Kidney Cortex / Q000378:metabolism*; D007700:Kinetics; D010281:Parathyroid Hormone / Q000378:metabolism*; D010740:Phospholipases / Q000494:pharmacology; D011485:Protein Binding; D011506:Proteins / Q000276:immunology / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects
chemical_list: D010281:Parathyroid Hormone; D011506:Proteins; D011956:Receptors, Cell Surface; D010740:Phospholipases