Quantification and distribution of Ca21-activated maxi K1 channels in rabbit distal colon
نویسندگان
چکیده
Grunnet, Morten, Hans-Günther Knaus, Christina Solander, and DanA. Klaerke. Quantification and distribution of Ca21-activated maxi K1 channels in rabbit distal colon. Am. J. Physiol. 277 (Gastrointest. Liver Physiol. 40): G22– G30, 1999.—The Ca21-activated maxi K1 channel is an abundant channel type in the distal colon epithelium, but nothing is known regarding the actual number and precise localization of these channels. The aim of this study has therefore been to quantify the maxi K1 channels in colon epithelium by binding of iberiotoxin (IbTX), a selective peptidyl ligand for maxi K1 channels. In isotope flux measurements 75% of the total K1 channel activity in plasma membranes from distal colon epithelium is inhibited by IbTX (K0.5 5 4.5 pM), indicating that the maxi K1 channel is the predominant channel type in this epithelium. Consistent with the functional studies, the radiolabeled double mutant 125I-IbTX-D19Y/Y36F binds to the colon epithelium membranes with an equilibrium dissociation constant of ,10 pM. The maximum receptor concentration values (in fmol/mg protein) for 125I-IbTX-D19Y/Y36F binding to colon epithelium are 78 for surface membranes and 8 for crypt membranes, suggesting that the maxi K1 channels are predominantly expressed in the Na1-absorbing surface cells, as compared with the Cl2-secreting crypt cells. However, aldosterone stimulation of this tissue induced by a low-Na1 diet does not change the total number of maxi K1 channels.
منابع مشابه
AGI July 40/1
Grunnet, Morten, Hans-Günther Knaus, Christina Solander, and DanA. Klaerke. Quantification and distribution of Ca21-activated maxi K1 channels in rabbit distal colon. Am. J. Physiol. 277 (Gastrointest. Liver Physiol. 40): G22– G30, 1999.—The Ca21-activated maxi K1 channel is an abundant channel type in the distal colon epithelium, but nothing is known regarding the actual number and precise loc...
متن کاملQuantification and distribution of Ca2+-activated maxi K+ channels in rabbit distal colon.
The Ca2+-activated maxi K+ channel is an abundant channel type in the distal colon epithelium, but nothing is known regarding the actual number and precise localization of these channels. The aim of this study has therefore been to quantify the maxi K+ channels in colon epithelium by binding of iberiotoxin (IbTX), a selective peptidyl ligand for maxi K+ channels. In isotope flux measurements 75...
متن کاملActivation of Ca21-activated K1 (maxi-K1) channel by angiotensin II in myocytes of the guinea pig ileum
Romero, Fernando, Bagnólia A. Silva, Viviane L. A. Nouailhetas, and Jeannine Aboulafia. Activation of Ca21activated K1 (maxi-K1) channel by angiotensin II in myocytes of the guinea pig ileum. Am. J. Physiol. 274 (Cell Physiol. 43): C983–C991, 1998.—We investigated the regulation of the Ca21-activated K1 (maxi-K1) channel by angiotensin II (ANG II) and its synthetic analog, [Lys2]ANG II, in fres...
متن کاملSmall-conductance Ca21-dependent K1 channels activated by ATP in murine colonic smooth muscle
Koh, S. D., G. M. Dick, and K. M. Sanders. Smallconductance Ca21-dependent K1 channels activated by ATP in murine colonic smooth muscle. Am. J. Physiol. 273 (Cell Physiol. 42): C2010–C2021, 1997.—The patch-clamp technique was used to determine the ionic conductances activated by ATP in murine colonic smooth muscle cells. Extracellular ATP, UTP, and 2-methylthioadenosine 58-triphosphate (2-MeSAT...
متن کاملThe b subunit of the high-conductance calcium-activated potassium channel contributes to the high-affinity receptor for charybdotoxin (transient expressionytoxin bindingyWestern blotsycrosslinking)
Transient expression of either a or a1b subunits of the high-conductance Ca21-activated K1 (maxi-K) channel has been achieved in COS-1 cells. Expression has been studied using charybdotoxin (ChTX), a peptidyl inhibitor that binds in the pore on the a subunit. Although some properties of monoiodotyrosine-ChTX (125I-ChTX) binding to membranes derived from each type of transfected cells appear to ...
متن کامل