title: Piscine PTHrP regulation of calcium and phosphate transport in winter flounder renal proximal tubule primary cultures.
abstract: Multiple factors control calcium (Ca(2+)) and inorganic phosphate (P(i)) transport in the fish nephron, and the recently discovered members of the piscine parathyroid hormone-like protein family are likely participants in such regulatory mechanisms. The effects of an NH(2)-terminal peptide (amino acids 1-34) of Takifugu rubripes parathyroid hormone-related protein, (1-34)PTHrP, on Ca(2+) and P(i) transport were investigated in winter flounder (Pseudopleuronectes americanus) proximal tubule cells in primary culture (fPTCs). RT-PCR performed on RNA extracted from fPTCs and from intact kidney tissue indicated that expression of PTHrP and types 1 and 3 PTH/PTHrP receptors occurred both in vivo and in vitro and that circulating levels of PTHrP measured by specific radioimmunoassay averaged 2.5 +/- 0.13 ng/ml. fPTC monolayers were mounted in Ussing chambers, and under neutral electrochemical conditions, addition of 10 nM (1-34)PTHrP to the basolateral side induced a slight increase in Ca(2+) transport rate from luminal to peritubular side, significantly stimulating net Ca(2+) reabsorption. (1-34)PTHrP also significantly increased the P(i) secretory flux, and slightly reduced P(i) reabsorption, evoking a significant increase in P(i) net secretion. This stimulatory effect was partially inhibited by bisindolylmaleimide, an inhibitor of protein kinase C. Incubation of ex vivo flounder renal tubules with (1-34)PTHrP resulted in apparent reduction of Na(+)-P(i) cotransporter type II (NaP(i)-II) protein in tubule membranes. PTHrP seems therefore to participate in the modulation of Ca(2+) and P(i) homeostasis by fish kidney.
authors.affiliation: Centre of Marine Sciences, Universidade do Algarve, 8005-139 Faro, Portugal. pmgg@ualg.pt
authors.forename: Pedro M
authors.initials: PM
authors.lastname: Guerreiro
authors.forename: Adelino V M
authors.initials: AV
authors.lastname: Canario
authors.forename: Deborah M
authors.initials: DM
authors.lastname: Power
authors.forename: J Larry
authors.initials: JL
authors.lastname: Renfro
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D017097:Electric Impedance; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D005432:Flounder / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D007211:Indoles / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008301:Maleimides / Q000494:pharmacology; D008564:Membrane Potentials; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000378:metabolism; D050610:Sodium-Phosphate Cotransporter Proteins, Type II / Q000378:metabolism
chemical_list: D029941:Fish Proteins; D007211:Indoles; D008301:Maleimides; D044162:Parathyroid Hormone-Related Protein; D010446:Peptide Fragments; D010710:Phosphates; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1; D050610:Sodium-Phosphate Cotransporter Proteins, Type II; C054296:parathyroid hormone-related protein (1-34); D011493:Protein Kinase C; C088060:bisindolylmaleimide; D002118:Calcium