Inhibition of P-type ATPases by [(dihydroindenyl)oxy]acetic acid (DIOA), a K+-Cl- cotransporter inhibitor

[(Dihydroindenyl)oxy] acetic acid (DIOA) has been used as a potent inhibitor of K+-Cl- cotransporter (IC50 = 10 mu M). Here we found that DIOA inhibited activities of P-type ATPases such as dog kidney Na+,K+-ATPase (IC50 = 53 mu M), hog gastric H+,K+-ATPase (IC50 = 97 mu M) and rabbit muscle Ca2+-ATPase (IC50 = 127 mu M). In the membrane preparation of the LLC-PKI cells stably expressing rabbit gastric H+,K+-ATPase, DIOA inhibited activities of the endogenous Na+,K+-ATPase (IC50=95 mu M) and the exogenous H+,K+-ATPase (IC50=75 mu M). 5-Nitro-2(3-phenylpropylamino)-benzoic acid (NPPB), a Cl- channel blocker, had no effects on the DIOA-elicited inhibition of the P-type ATPases. These findings suggest that lower concentration of DIOA (< 20-30 mu M) should be used for evaluation of the activity of K+-Cl- cotransporter without affecting the activities of coexisting Na+,K+-ATPase and/or H+,K+-ATPase in cells. (c) 2007 Elsevier B.V. All rights reserved.