EFFECT OF ADENOSINE ON THE OUABAIN-INSENSITIVE NA-ATPASE ACTIVITY FROM BASOLATERAL MEMBRANE OF THE PROXIMAL TUBULE()

The regulation of the furosemide-sensitive Na+-ATPase activity and oua bain-sensitive (Na+ + K+)ATPase activities from proximal tubules by ad enosine was investigated. When the concentration of adenosine was incr eased the furosemide-sensitive ATPase activity decreased with maximal inhibition at 10(-8) M (56% of inhibition). However, the (Na+ + K+)ATP ase activity was not affected by adenosine. Theophylline, an antagonis t of P-1 adenosine receptor, completely reversed the effect of adenosi ne on the furosemide-sensitive ATPase activity in a dose-response mann er. The adenosine effect was mimicked by N-6-cyclohexyladenosine (CHA) , an agonist for A(1) adenosine receptor. 5'-N-ethylcarboxamideadenosi ne (NECA), an agonist for A(1) adenosine receptor, did not affect the furosemide-sensitive ATPase activity. When adenosine was used in the p resence of 1 mu g ml(-1) pertussis toxin, a Gi protein inhibitor, no c hange in the furosemide-sensitive ATPase activity was observed. The ad dition of 1 nM cholera toxin increased the Nai-ATPase activity by 60%. Adenosine decreased the cholera toxin stimulated Na+-ATPase in 42%. s imilar to the effect observed in the absence of cholera toxin. Dibutyr yl-cAMP reversed the effect of adenosine in a dose dependent manner wh ile the protein kinase A peptide inhibitor mimicked it. These data are compatible with a modulatory effect of adenosine on the Na+-ATPase ac tivity via A(1) subtype receptor. (C) 1997 Elsevier Science B.V.