In a preceding study we showed that the highly negative resting membrane potential of rat adrenal glomerulosa cells is related to background potassium channel(s), which belong to the two-pore domain channel family. TWIK-related acid-sensitive K ؉ channel (TASK-1) expression was found in glomerulosa tissue, and the currents elicited by injection of glomerulosa mRNA (I glom ) or TASK-1 cRNA (I TASK-1 ) showed remarkable similarity in Xenopus laevis oocytes. However, based on the different

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... ity of these currents to acidification, we concluded that TASK-1 may be responsible for a maximum of 25% of the weakly pH-dependent glomerulosa background K ؉ current. Here we demonstrate that TASK-3, a close relative of TASK-1, is expressed abundantly in glomerulosa cells. Northern blot detected TASK-3 Abbreviations: EC, Extracellular; 2P, two-pore; RR, ruthenium red; TASK, TWIK-related acid-sensitive K ϩ channel.