The effects of nucleotides and potassium channel openers on the SUR2A/Kir6.2 complex K super(+) channel expressed in a mammalian cell line, HEK293T cells

• Published in: Pflügers Archiv 1998-03, Vol.435 (5), p.595-603
• Main Authors: Okuyama, Yuji, Yamada, Mitsuhiko, Kondo, Chikako, Satoh, Eisaku, Isomoto, Shojiro, Shindo, Takashi, Horio, Yoshiyuki, Kitakaze, Masafumi, Hori, Masatsugu, Kurachi, Y
• Format: Article
• Language: English
• Subjects: ATP
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s004240050559

The effects of potassium channel opening drugs and intracellular nucleotides on the ATP-sensitive K+ (K sub(ATP)) channel composed of SUR2A and Kir6.2 in HEK293T cells were examined using the patch-clamp technique. The SUR2A/Kir6.2 channel was activated effectively by pinacidil, marginally by nicorandil but not by diazoxide. The pinacidil-activated channel currents were inhibited by glibenclamide with a K sub(i) value of 160 nM. Upon formation of inside-out (I-O) patches, spontaneous openings of the channels appeared, which were inhibited by intracellular ATP (ATP sub(i)) equipotently in the presence and in the absence of intracellular Mg super(2+) (Mg super(2+) sub(i)). The channel activity ran-down gradually in I-O patches. The run-down channels could be reactivated by ATP sub(i) only in the presence of Mg super(2+) sub(i). Uridine 5'-diphosphate (UDP) antagonized the ATP sub(i)-mediated inhibition of the channel activity before run-down. After run-down, UDP activated the channel without antagonizing ATP sub(i)-mediated channel inhibition. Thus, the SUR2A/Kir6.2 reproduced the major properties of the native cardiac K sub(ATP) channel well in terms of nucleotide regulation and pharmacology, and therefore can be a useful tool with which to elucidate the molecular mechanisms characterizing the K sub(ATP) channel.