Luminal and contraluminal action of 1-34 and 3-34 PTH peptides on renal type IIa Na-P(i) cotransporter.
Parathyroid hormone (PTH) inhibits proximal tubular reabsorption of P(i) by retrieval of type IIa Na-P(i) cotransporters (NaPi-IIa) from the brush-border membrane (BBM). We analyzed by immunohistochemistry whether PTH analogs, signaling through either protein kinase A (PKA) and C (PKC; 1-34 PTH) or only PKC (3-34 PTH), elicit in rat kidney in vivo or in the perfused murine proximal tubule in vitro a retrieval of NaPi-IIa and whether pharmacological agonists or inhibitors of these kinases are able to either mimic or interfere with these PTH effects. Treatment with either 1-34 or 3-34 PTH downregulated NaPi-IIa in rat kidney. In isolated murine proximal tubules 1-34 PTH was effective when added to either the apical or basolateral perfusate, whereas 3-34 PTH acted only via the luminal perfusate. These effects were mimicked by an activation of PKA with 8-bromoadenosine 3',5'-cyclic monophosphate or PKC with 1, 2-dioctanoylglycerol. The luminal action of both PTH peptides was blocked by inhibition of the PKC pathway (calphostin C), whereas the basolateral effect of 1-34 PTH was completely abolished by inhibiting both pathways (H-89 and calphostin C). These results suggest that 1) NaPi-IIa can be internalized by cAMP-dependent and -independent signaling mechanisms; 2) functional PTH receptors are located in both membrane domains; and 3) apical PTH receptors may preferentially initiate the effect through a PKC-dependent mechanism.
Traebert
M
M
Institutes of Anatomy and Physiology, University of Zurich, CH-8057 Zurich, Switzerland.
Völkl
H
H
Biber
J
J
Murer
H
H
Kaissling
B
B
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D010477:Perfusion; D010710:Phosphates / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D010281:Parathyroid Hormone; D010446:Peptide Fragments; D010710:Phosphates; C493555:Slc34a1 protein, mouse; C493556:Slc34a1 protein, rat; D050608:Sodium-Phosphate Cotransporter Proteins; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D027981:Symporters; C031617:parathyroid hormone (3-34); D012964:Sodium; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C