– VU0134992 (VU 0134992) is a potent, selective blocker of the inward rectifier potassium channel Kir4.1 (KCNJ10) with IC50 of 0.97 uM in whole-cell patch clamp electrophysiology assays; displays 9-fold selectivity for homomeric Kir4.1 over Kir4.1/5.1 concatemeric channels (IC50=9 uM) at -120 mV; VU0134992 is greater than 30-fold selective for Kir4.1 over Kir1.1, Kir2.1, and Kir2.2, is weakly active toward Kir2.3, Kir6.2/SUR1, and Kir7.1, and is equally active toward Kir3.1/3.2, Kir3.1/3.4, and Kir4.2 in Tl+ flux assays; causes dose-dependent diuresis, natriuresis, and kaliuresis in rats after oral treatment; VU0134992 represents the first in vivo-active tool compound for probing the therapeutic potential of Kir4.1 as a novel diuretic target for the treatment of hypertension.