title: Comparison of renal and osseous binding of parathyroid hormone and hormonal fragments.
abstract: We compared receptor binding and adenylate cyclase stimulation of intact bovine parathyroid hormone (bPTH)-(1-84) and the synthetic amino-terminal fragments, bPTH-(1-34) and rat PTH (rPTH)-(1-34). Radioligands for binding studies were prepared by the lactoperoxidase technique and purified by high-pressure liquid chromatography. In both canine renal membranes and cloned rat osteosarcoma cells the amino-terminal fragments bound to a single order of sites; the affinity of rPTH-(1-34) exceeded that of bPTH-(1-34), correlating with its higher potency in stimulating adenylate cyclase. In studies with oxidized bPTH-(1--84), the middle and carboxyl regions of intact PTH were found to bind to both tissues but with higher affinity to osteosarcoma cells than to renal membranes. Our results demonstrate that rPTH-(1--34) is the most favorable probe of amino-terminal PTH binding and the most potent of the PTH peptides in stimulating renal and osseous adenylate cyclase. The results also show that midregion and carboxyl determinants within intact PTH contribute to hormone binding, which does not correlate with adenylate cyclase activation and appears more significant for skeletal than for renal binding.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002999:Clone Cells; D004285:Dogs; D004789:Enzyme Activation; D007457:Iodine Radioisotopes; D007672:Kidney Cortex / Q000201:enzymology / Q000378:metabolism*; D008954:Models, Biological; D012516:Osteosarcoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D010281:Parathyroid Hormone / Q000378:metabolism*; D051381:Rats
chemical_list: D007457:Iodine Radioisotopes; D010281:Parathyroid Hormone; D000262:Adenylyl Cyclases