title: Effect of adenosine triphosphate on phosphate uptake in renal proximal tubule cells: involvement of PKC and p38 MAPK.
abstract: ATP has been known to act as an extracellular signal and to be involved in various functions of kidney. Renal proximal tubular reabsorption of phosphate (Pi) contributes to the maintenance of phosphate homeostasis, which is regulated by Na+/Pi cotransporter. However, the effects of ATP on Na+/Pi cotransporters were not elucidated in proximal tubule cells (PTCs). Thus, the effects of ATP on Na+/Pi cotransporter and its related signal pathways are examined in the primary cultured renal PTCs. In the present study, ATP inhibited Pi uptake in a time (> 1 h) and dose (>10(-6)M) dependent manner. ATP-induced inhibition of Pi uptake was correlated with the decrease of type II Na+/Pi cotransporter mRNA. ATP-induced inhibition of Pi uptake may be mediated by P2Y receptor activation, since suramin (non-specific P2 receptor antagonist) and RB-2 (P2Y receptor antagonist) blocked it. ATP-induced inhibition of Pi uptake was blocked by neomycin, U73122 (phospholipase C (PLC) inhibitors), bisindolylmaleimide I, H-7, and staurosporine (protein kinase C (PKC) inhibitors), suggesting the role of PLC/PKC pathway. ATP also increased inositol phosphates (IPs) formation and induced PKC translocation from cytosolic fraction to membrane fraction. In addition, ATP-induced inhibition of Pi uptake was blocked by SB 203580 [a p38 mitogen activated protein kinase (MAPK) inhibitor], but not by PD 98059 (a p44/42 MAPK inhibitor). Indeed, ATP induced phosphorylation of p38 MAPK, which was not blocked by PKC inhibitor. In conclusion, ATP inhibited Pi uptake via PLC/PKC as well as p38 MAPK in renal PTCs.
authors.affiliation: Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
authors.forename: Yun Jung
authors.initials: YJ
authors.lastname: Lee
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Park
authors.forename: Tae Oh
authors.initials: TO
authors.lastname: Jeung
authors.forename: Kee Won
authors.initials: KW
authors.lastname: Kim
authors.forename: Jang Hern
authors.initials: JH
authors.lastname: Lee
authors.forename: Ho Jae
authors.initials: HJ
authors.lastname: Han
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D047908:Intracellular Signaling Peptides and Proteins / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D010710:Phosphates / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D010738:Type C Phospholipases / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D010710:Phosphates; D058906:Purinergic P1 Receptor Agonists; D058915:Purinergic P1 Receptor Antagonists; D012333:RNA, Messenger; D018047:Receptors, Purinergic P1; C015482:protein kinase modulator; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D048051:p38 Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases