Piscine PTHrP regulation of calcium and phosphate transport in winter flounder renal proximal tubule primary cultures

Am J Physiol Regul Integr Comp Physiol. 2010 Aug;299(2):R603-11. doi: 10.1152/ajpregu.00509.2009. Epub 2010 May 19.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biological Transport
  • Calcium / metabolism*
  • Cells, Cultured
  • Electric Impedance
  • Fish Proteins / genetics
  • Fish Proteins / metabolism*
  • Flounder / genetics
  • Flounder / metabolism*
  • Gene Expression Regulation
  • Indoles / pharmacology
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism*
  • Kinetics
  • Maleimides / pharmacology
  • Membrane Potentials
  • Parathyroid Hormone-Related Protein / genetics
  • Parathyroid Hormone-Related Protein / metabolism*
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism*
  • Phosphates / metabolism*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism
  • Protein Kinase Inhibitors / pharmacology
  • RNA, Messenger / metabolism
  • Receptor, Parathyroid Hormone, Type 1 / metabolism
  • Sodium-Phosphate Cotransporter Proteins, Type II / metabolism

Substances

  • Fish Proteins
  • Indoles
  • Maleimides
  • Parathyroid Hormone-Related Protein
  • Peptide Fragments
  • Phosphates
  • Protein Kinase Inhibitors
  • RNA, Messenger
  • Receptor, Parathyroid Hormone, Type 1
  • Sodium-Phosphate Cotransporter Proteins, Type II
  • parathyroid hormone-related protein (1-34)
  • Protein Kinase C
  • bisindolylmaleimide
  • Calcium