Short- and long-term A3 adenosine receptor activation inhibits the Na+/H+ exchanger NHE3 activity and expression in opossum kidney cells
✍ Scribed by Francesca Di Sole; Robert Cerull; Victor Babich; Valeria Casavola; Corinna Helmle-Roth; Gerhard Burckhardt
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 480 KB
- Volume
- 216
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
The renal function of the A~3~ adenosine receptor (A3AR) is poorly characterized. In this study, we report that the A3AR‐selective agonist, 1‐[2‐chloro‐6‐[[(3‐iodophenyl)methyl]amino]‐9__H__‐purine‐9‐yl]‐1‐deoxy‐N‐methyl‐b‐D‐ribofuranuronamide (2‐Cl‐IBMECA) regulates the Na^+^/H^+^ exchanger‐3 (NHE3) in a dose‐ and time‐dependent fashion. In opossum kidney (OK) cells, 2‐Cl‐IBMECA at high (10^−6^ M) and low (10^−8^ M) dose inhibits NHE3 by a multiphasic time course with an acute phase of NHE3 inhibition from 15 min to 1 h, followed by a chronic phase of NHE3 inhibition from 24 to 48 h. Pre‐incubation with either the selective A3AR‐antagonist MRS1523 (10^−7^ M) or the protein kinase C inhibitor, Calphostin C (10^−8^ M) completely blocked 10^−6^ M 2‐Cl‐IBMECA‐induced acute (15 min) and chronic (24 h) phases of NHE3 inhibition. In contrast, the acute inhibitory phase (15 min) of 10^−8^ M 2‐Cl‐IBMECA was completely prevented only when Calphostin C (10^−8^ M) was added in conjunction with the protein kinase A inhibitor, H89 (10^−7^ M). Acute (15 or 30 min depending on the A3AR‐agonist concentration) A3AR‐dependent inhibition of NHE3 activity was accompanied by decrease in cell surface NHE3 protein with no change in total NHE3 antigen. Chronic (24 h) A3AR‐mediated down‐regulation of NHE3 was associated with reduction of surface NHE3, decreased total NHE3 protein (70%) and a paradoxical rise of NHE3 RNA (40%). In summary, these results indicate that A3AR directly regulates NHE3 at multiple levels in a complex pattern. A3AR‐dependent short‐ and long‐term inhibition of NHE3 may be a fundamental mechanism of net sodium and fluid balance. J. Cell. Physiol. 216: 221–233, 2008. © 2008 Wiley‐Liss, Inc.