Evidence for basolateral P2Y(6) receptors along the rat proximal tubule: functional and molecular characterization.
In this study, the distribution of P2Y(6) receptor mRNA in rat nephron segments was investigated and a functional approach was used to analyze basolateral protein expression. Reverse transcription-PCR studies revealed more intense expression of P2Y(6) receptor mRNA in the proximal tubule and the thick ascending limb of Henle's loop, less intense expression in the thin descending limb and the cortical and outer medullary collecting ducts, and no detectable expression in either the thin ascending limb or the inner medullary collecting duct. Dose-dependent calcium responses to basolateral administration of UDP (a selective agonist for the P2Y(6) receptor) were observed in the proximal tubule but not in any of the other segments studied. In the proximal tubule, intracellular calcium concentration changes induced by UDP were associated with increased production of inositol phosphates, as were those induced by ATP and norepinephrine. However, UDP-induced intracellular calcium concentration changes were different, exhibiting no plateau after the initial peak; moreover, a single stimulation with a high concentration of UDP induced full desensitization of the UDP-sensitive calcium pathway but did not alter the responsiveness of the proximal tubule to ADP (a specific P2Y(1) receptor agonist), ATP or norepinephrine. In summary, this report demonstrates that P2Y(6) receptor mRNA is expressed in most segments of the rat nephron but that basolateral expression of the protein is restricted to the proximal tubule, where the receptor is coexpressed with the P2Y(1) receptor. The differences in the distributions of P2Y(6) receptor mRNA and UDP responses may indicate the presence of luminal receptors in other nephron segments.
Bailey
Matthew A
MA
Centre for Nephrology, University College London, London, United Kingdom.
Imbert-Teboul
Martine
M
Centre National de la Recherche Scientifique URA 1859, CEA Saclay, Gif sur Yvette, France.
Turner
Clare
C
Centre for Nephrology, University College London, London, United Kingdom.
Srai
S Kaila
SK
Department of Biochemistry and Molecular Biology, University College London, London, United Kingdom.
Burnstock
Geoffrey
G
Autonomic Neuroscience Institute, Royal Free and University College Medical School, University College London, London, United Kingdom.
Unwin
Robert J
RJ
Centre for Nephrology, University College London, London, United Kingdom.|Autonomic Neuroscience Institute, Royal Free and University College Medical School, University College London, London, United Kingdom.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D009399:Nephrons / Q000378:metabolism; D009994:Osmolar Concentration; D010716:Phosphatidylinositols / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D014018:Tissue Distribution; D014530:Uridine Diphosphate / Q000494:pharmacology
D010716:Phosphatidylinositols; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; C099845:purinoceptor P2Y6; D014530:Uridine Diphosphate; D002118:Calcium