Adenosine inhibits the transfected Na+-H+ exchanger NHE3 in Xenopus laevisrenal epithelial cells (A6/C1)

Citation
F. Di Sole et al., Adenosine inhibits the transfected Na+-H+ exchanger NHE3 in Xenopus laevisrenal epithelial cells (A6/C1), J PHYSL LON, 515(3), 1999, pp. 829-842
Citations number
42
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physiology
Journal title
JOURNAL OF PHYSIOLOGY-LONDON
ISSN journal
0022-3751 → ACNP
Volume
515
Issue
3
Year of publication
1999
Pages
829 - 842
Database
ISI
SICI code
0022-3751(19990315)515:3<829:AITTNE>2.0.ZU;2-H
Abstract
1. Adenosine influences the vectorial transport. of Na+ and HCO3- across ki dney epithelial cells. However, its action on effector proteins, such as th e Na+-H+ exchanger NHE3, an epithelial brush border isoform of the Na+-H+ e xchanger (NHE) gene family: is not yet defined, 2. The present study was conducted in Xenopus laevis distal nephron A6 epit helia which express both an apical adenosine receptor of the A(1) type (cou pled to protein kinase C (PKC)) and a basolateral receptor of the A(2) type (coupled to protein kinase A (PKA)). The untransfected A6 cell line expres ses a single NHE type (XNHE) which is restricted to the basolateral membran e and which is activated by PKA. 3. A6 cell lines were generated which express exogenous rat NHE3. Measureme nts of side-specific pH(i) recovery from acid loads in the presence of HOE6 94 (an inhibitor with differential potency towards individual NHE isoforms) detected an apical resistant Na+-H+ exchange only in transfected cell line s. The sensitivity of the basolateral NHE to HOE694 was unchanged, suggesti ng that exogenous NHE3 was restricted to the apical membrane. 4. Stimulation of the apical A(1) receptor with N-6-cyclopentyladenosine (C PA) inhibited both epical NHE3 and basolateral;XNHE. These effects were mim icked by the addition of the protein kinase C (PKC) activator phorbol 12-my ristate 13-acetate (PMA) and partially prevented by the PKC inhibitor calph ostin C which also blocked the effect of PMA. 5. Stimulation of the basolateral A(2) receptor with CPA inhibited apical N HE3 and stimulated basolateral XNHE. These effects were mimicked by 8-bromo -cAMP and partially prevented by the PKA inhibitor H89 which entirely block ed the effect of 8-bromo-cAMP. 6. In conclusion, CPA inhibits rat NHE3 expressed apically in A6 epithelia via both the apical PKC-coupled A(1) and the basolateral PKA-coupled A(2) a denosine receptors.