Luminal P2Y2 Receptor-Mediated Inhibition of Na+ Absorption ... : Journal of the American Society of Nephrology (original) (raw)

Cell and Transport Physiology

Luminal P2Y2 Receptor-Mediated Inhibition of Na+ Absorption in Isolated Perfused Mouse CCD

Lehrmann, Heiko*; Thomas, Jo[Combining Diaeresis]rg*; Kim, Sung Joon†; Jacobi, Christoph*; Leipziger, Jens*

*Physiologisches Institut, Albert-Ludwigs-Universita[Combining Diaeresis]t, Hermann-Herder-Straβe 7, 79104 Freiburg, Germany; †Department of Physiology, Sungkyunkwan University School of Medicine, Suwon 440-746, South Korea.

Correspondence to Jens Leipziger, Institute of Physiology, Ole Worms Alle[Combining Acute Accent] 160, 8000 Aarhus C, Denmark. Phone: +45-89-422800; Fax: +45-86-129065; E-mail: [email protected]

Accepted September 21, 2001

Received March 12, 2001

Abstract

ABSTRACT. Extracellular nucleotides regulate renal transport. A luminal P2Y2 receptor in mouse cortical collecting duct (CCD) principal cells has been demonstrated elsewhere. Herein the effects of adenosine triphosphate (ATP) and uridine triphosphate (UTP) on electrogenic Na+ absorption in perfused CCD of mice kept on a low-NaCl diet were investigated. Simultaneously, transepithelial voltage (_V_te), transepithelial resistance (_R_te), and fura-2 [Ca2+]i fluorescence were measured. Baseline parameters were _V_te, −16.5 ± 1.2 mV; _R_te, 80.8 ± 7.1 Ω cm2; and equivalent short-circuit current (_I_sc), −261.0 ± 25.1 μA/cm2 (n = 45). Amiloride (10 μM) almost completely inhibited _I_sc to −3.9 ± 3.8 μA/cm2 (n = 10). Luminal ATP (100 μM) reduced _V_te from −16.5 ± 2.1 to −12.5 ± 1.93 and increased _R_te from 113.1 ± 16.2 to 123.8 ± 16.7 Ω cm2, which resulted in a 31.7% inhibition of amiloride-sensitive _I_sc (n = 12). Similarly, luminal UTP reversibly reduced _V_te from −22.0 ± 2.1 to −13.6 ± 2.1 mV and increased _R_te from 48.4 ± 5.3 to 59.2 ± 7.1 Ω cm2, which resulted in 49.1% inhibition of Na+ absorption (n = 6). In parallel, luminal ATP and UTP elevated [Ca2+]i in CCD, increasing the fura-2 ratio by 2.7 ± 0.7 and 4.0 ± 1.2, respectively. Basolateral ATP and UTP (100 μM) also inhibited amiloride-sensitive _I_sc by 21.8 (n = 14) and 20.1% (n = 8), respectively. Inhibition of luminal nucleotide-induced [Ca2+]i increase by Ca2+ store depletion with cyclopiazonic acid (3 μM) did not affect nucleotide-mediated inhibition of Na+ transport (n = 7). No evidence indicated the activation of a luminal Ca2+-activated Cl− conductance, a phenomenon previously shown in M-1 CCD cells (J Physiol 524: 77–99, 2000). In essence, these data indicate that luminal ATP and UTP, most likely via P2Y2 receptors, mediate inhibition of amiloride-sensitive Isc in perfused mouse CCD. This inhibition appears to occurs independently of an increase of cytosolic Ca2+.