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Adenosine inhibits the transfected Na + ‐H + exchanger NHE3 in Xenopus laevis renal epithelial cells (A6/C1)
Author(s) -
Sole Francesca,
Casavola Valeria,
Mastroberardino Luca,
Verrey François,
Moe Orson W.,
Burckhardt Gerhard,
Murer Heini,
HelmleKolb Corinna
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.829ab.x
Subject(s) - xenopus , transfection , chemistry , adenosine , sodium–hydrogen antiporter , microbiology and biotechnology , biology , gene , biochemistry , sodium , organic chemistry
1 Adenosine influences the vectorial transport of Na + and HCO 3 − across kidney epithelial cells. However, its action on effector proteins, such as the Na + ‐H + exchanger NHE3, an epithelial brush border isoform of the Na + ‐H + exchanger (NHE) gene family, is not yet defined. 2 The present study was conducted in Xenopus laevis distal nephron A6 epithelia which express both an apical adenosine receptor of the A 1 type (coupled 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 expresses a single NHE type ( X NHE) which is restricted to the basolateral membrane and which is activated by PKA. 3 A6 cell lines were generated which express exogenous rat NHE3 . Measurements of side‐specific pH i recovery from acid loads in the presence of HOE694 (an inhibitor with differential potency towards individual NHE isoforms) detected an apical resistant Na + ‐H + exchange only in transfected cell lines. The sensitivity of the basolateral NHE to HOE694 was unchanged, suggesting that exogenous NHE3 was restricted to the apical membrane. 4 Stimulation of the apical A 1 receptor with N 6 ‐cyclopentyladenosine (CPA) inhibited both apical NHE3 and basolateral X NHE. These effects were mimicked by the addition of the protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA) and partially prevented by the PKC inhibitor calphostin C which also blocked the effect of PMA. 5 Stimulation of the basolateral A 2 receptor with CPA inhibited apical NHE3 and stimulated basolateral X NHE. These effects were mimicked by 8‐bromo‐cAMP and partially prevented by the PKA inhibitor H89 which entirely blocked 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 adenosine receptors.