Ph-dependent modulation of the cloned renal k+ channel, romk.
McNicholas, Carmel M., Gordon G. Macgregor, Leon D. Islas, Yinhai
Yang, Steven C. Hebert and Gerhard Giebisch.
1 Department of Cellular & Molecular Physiology, Yale University
School of Medicine, New Haven, CT 06520, 2 Present Address:
Department of Cardiology, Children's Hospital, 320 Longwood Ave.,
Enders 1309, Boston, MA 02115, 3 Division of Nephrology, Vanderbilt
University School of Medicine, S3223 MCN, Nashville, TN 37322
-2372
APStracts 5:0156F, 1998.
pH is an important modulator of the low conductance ATP-sensitive K+
channel of the distal nephron. To examine the mechanism of
interaction of protons (H+) with the channel forming protein, we
expressed the cloned renal K+ channel, ROMK (Kir1.x), in Xenopus
oocytes and examined the response to varied concentrations of protons
both in the presence and in the absence of ATP. Initial experiments
were performed on inside-out patches in the absence of ATP in Mg2+
-free solution that prevents channel rundown. A steep sigmoidal
relationship was shown between bath pH and ROMK1 or ROMK2 channel
function with intracellular acidification reducing channel activity.
We calculated values for pK = 7.18 and 7.04 and Hill coefficients =
3.1 and 3.3 for ROMK1 and ROMK2, respectively.
Received 11 September 1997; accepted in final form 3 Septmeber
1998.
APS Manuscript Number F294-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 21 September 1998