Effects of luminal flow and nucleotides on [Ca(2+)](i) in rabbit cortical collecting duct.
Nucleotide binding to purinergic P2 receptors contributes to the regulation of a variety of physiological functions in renal epithelial cells. Whereas P2 receptors have been functionally identified at the basolateral membrane of the cortical collecting duct (CCD), a final regulatory site of urinary Na(+), K(+), and acid-base excretion, controversy exists as to whether apical purinoceptors exist in this segment. Nor has the distribution of receptor subtypes present on the unique cell populations that constitute Ca(2+) the CCD been established. To examine this, we measured nucleotide-induced changes in intracellular Ca(2+) concentration ([Ca(2+)](i)) in fura 2-loaded rabbit CCDs microperfused in vitro. Resting [Ca(2+)](i) did not differ between principal and intercalated cells, averaging approximately 120 nM. An acute increase in tubular fluid flow rate, associated with a 20% increase in tubular diameter, led to increases in [Ca(2+)](i) in both cell types. Luminal perfusion of 100 microM UTP or ATP-gamma-S, in the absence of change in flow rate, caused a rapid and transient approximately fourfold increase in [Ca(2+)](i) in both cell types (P < 0.05). Luminal suramin, a nonspecific P2 receptor antagonist, blocked the nucleotide- but not flow-induced [Ca(2+)](i) transients. Luminal perfusion with a P2X (alpha,beta-methylene-ATP), P2X(7) (benzoyl-benzoyl-ATP), P2Y(1) (2-methylthio-ATP), or P2Y(4)/P2Y(6) (UDP) receptor agonist had no effect on [Ca(2+)](i). The nucleotide-induced [Ca(2+)](i) transients were inhibited by the inositol-1,4,5-triphosphate receptor blocker 2-aminoethoxydiphenyl borate, thapsigargin, which depletes internal Ca(2+) stores, luminal perfusion with a Ca(2+)-free perfusate, or the L-type Ca(2+) channel blocker nifedipine. These results suggest that luminal nucleotides activate apical P2Y(2) receptors in the CCD via pathways that require both internal Ca(2+) mobilization and extracellular Ca(2+) entry. The flow-induced rise in [Ca(2+)](i) is apparently not mediated by apical P2 purinergic receptor signaling.
Woda
Craig B
CB
Department of Pediatrics, Mount Sinai School of Medicine, New York, New York 10029-6574, USA.
Leite
Maurilo
M
Rohatgi
Rajeev
R
Satlin
Lisa M
LM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000187:drug effects; D005260:Female; D017629:Gap Junctions / Q000187:drug effects; D007672:Kidney Cortex / Q000378:metabolism; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology; D009711:Nucleotides / Q000494:pharmacology*; D058919:Purinergic P2 Receptor Antagonists; D011817:Rabbits; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology; D013498:Suramin / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
D001896:Boron Compounds; D020746:Calcium Channels, L-Type; D009711:Nucleotides; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; C022571:adenosine 5'-O-(3-thiotriphosphate); D013498:Suramin; D019284:Thapsigargin; D000255:Adenosine Triphosphate; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D002118:Calcium; D014544:Uridine Triphosphate