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EDITORIAL FOCUS

Low salt intake increases adenosine type 1 receptor expression and function in the rat proximal tubule

Division of Nephrology and Hypertension, Department of Medicine, Georgetown University, Washington, District of Columbia

Submitted 5 February 2008 ; accepted in final form 29 April 2008

Adenosine mediates Na⁺ reabsorption in the proximal tubule (PT) and other segments by activating adenosine type 1 receptors (A1-AR). We tested the hypothesis that A1-AR in the PT is regulated by salt intake and participates in the kidney adaptation to changes in salt intake. Absolute fluid reabsorption (J_v) was measured by direct in vivo microperfusion and recollection in rats maintained on low (LS; 0.03% Na, wt/wt)-, normal (NS; 0.3% Na)-, and high-salt (HS; 3.0% Na) diets for 1 wk. The effect of microperfusion of BG9719 a highly selective inhibitor of A1-ARs or adenosine deaminase (AD), which metabolizes adenosine, was measured in each group. J_v was higher in PT from LS rats (LA: 2.8 ± 0.2 vs. NS: 2.1 ± 0.2 nl·min^–1·mm^–1, P < 0.001). J_v in HS rats was not different from NS. BG9719 reduced J_v in LS rats by 66 ± 6% (LS: 2.8 ± 0.2 vs LS+CVT: 1.3 ± 0.3 nl·min^–1·mm^–1, P < 0.001), which was greater than its effect in NS (45 ± 4%) or HS (41 ± 4%) rats. AD reduced J_v similarly, suggesting that A1-ARs are activated by local production of adenosine. Expression of A1-AR mRNA and protein was higher (P < 0.01) in microdissected PTs in LS rats compared with NS and HS. We conclude that A1-ARs in the PT are increased by low salt intake and that A1-AR participates in the increased PT reabsorption of solute and fluid in response to low salt intake.

fluid reabsorption; microperfusion

This article has been cited by other articles:

				H. Castrop Modulation of adenosine receptor expression in the proximal tubule: a novel adaptive mechanism to regulate renal salt and water metabolism Am J Physiol Renal Physiol, July 1, 2008; 295(1): F35 - F36. [Full Text] [PDF]