title: Calcitonin inhibits phosphate uptake in opossum kidney cells stably transfected with a porcine calcitonin receptor.
abstract: Calcitonin (CT), and PTH and PTH-related protein (PTHrP) stimulated urinary excretion of phosphate is brought about through inhibition of Na/P04 cotransport in proximal renal tubules. PTH/PTHrP receptors linked to inhibition of phosphate uptake have been characterized in a renal tubular cell line from the American opossum (OK). Specific binding of [125I]salmon CT (sCT) to OK cells was not recognized, but 1 microM sCT stimulated cAMP accumulation 10-fold and reduced phosphate uptake by 7 +/- 2% (P < 0.05). The responses were amplified in OK cells stably transfected with a cloned CT receptor from a porcine LLC-PK1 kidney cell line. The transfected cells expressed 20,000 CT receptors per cell with a Kd of 0.05 nM and an EC50 of cAMP accumulation of 6.2 nM; maximal cAMP stimulation in response to 1 microM sCT was 259-fold (P < 0.01). Phosphate uptake was inhibited by 35 +/- 4% in response to 1 microM sCT and by 34 +/- 3% to 1 microM chicken PTHrP(1-36) (P < 0.01). Half-maximal inhibition was obtained with 0.63 +/- 0.30 nM sCT and with 1.39 +/- 0.67 nM chicken PTHrP(1-36). The inhibition of [125I]sCT binding by nonlabeled human amylin required about 5000-fold higher concentrations than those of sCT, and human calcitonin gene-related peptide-I (CGRP) at up to 1 microM did not affect [125I]sCT binding. The rank order of potencies with respect to stimulation of cAMP accumulation and inhibition of phosphate transport of sCT, amylin and CGRP was the same. This is the first report linking a cloned CT receptor to inhibition of phosphate transport in a renal proximal tubular cell.
authors.affiliation: Department of Orthopedic Surgery, University of Zurich, Switzerland.
authors.forename: R
authors.initials: R
authors.lastname: Muff
authors.forename: M
authors.initials: M
authors.lastname: Kaufmann
authors.forename: W
authors.initials: W
authors.lastname: Born
authors.forename: J A
authors.initials: JA
authors.lastname: Fischer
mesh_terms: D000818:Animals; D002116:Calcitonin / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D007668:Kidney / Q000378:metabolism*; D009893:Opossums; D044162:Parathyroid Hormone-Related Protein; D010710:Phosphates / Q000378:metabolism*; D011506:Proteins / Q000494:pharmacology; D018003:Receptors, Calcitonin / Q000235:genetics / Q000502:physiology*; D013552:Swine; D014162:Transfection
chemical_list: D044162:Parathyroid Hormone-Related Protein; D010710:Phosphates; D011506:Proteins; D018003:Receptors, Calcitonin; D002116:Calcitonin; D000242:Cyclic AMP