Two types of ATP-sensitive potassium channels in rat portal vein smooth muscle cells
Version of Record online: 19 JUL 2012
1996 British Pharmacological Society
British Journal of Pharmacology
Volume 118, Issue 1, pages 105–114, May 1996
How to Cite
Zhang, H.-L. and Bolton, T.B. (1996), Two types of ATP-sensitive potassium channels in rat portal vein smooth muscle cells. British Journal of Pharmacology, 118: 105–114. doi: 10.1111/j.1476-5381.1996.tb15372.x
- Issue online: 19 JUL 2012
- Version of Record online: 19 JUL 2012
- Received August 14, 1995; Revised December 4, 1995; Accepted January 16, 1996
- Smooth muscle;
- ATP-sensitive K channels;
- 1. Single-channel recordings were made from single, enzymatically isolated smooth muscle cells of rat portal vein by the patch-clamp technique.
- 2. Unitary potassium currents were identified through two types of K-channels with conductances in 60:130 mM K-gradient of 50 and 22 pS; these are referred to as LK and MK channels respectively.
- 3. The LK channels became extremely active if isolated patches were created into nucleotide-free solution; activity was inhibited by ATP applied to the inner surface of the patch with a half maximal inhibition (Ki) of 11–23 μm. Channel activity declined and disappeared with time and could be regenerated by a brief application of Mg-ATP or a nucleoside diphosphate such as UDP (in the presence of Mg). LK channel activity was rarely stimulated by levcromakalim and not by pinacidil (K-channel openers, KCOs) but was blocked by glibenclamide.
- 4. Activity of MK channels declined if isolated patches were created into nucleotide free solution; activity reappeared if UDP or ATP alone (in the presence of Mg) was applied; pinacidil or levcromakalim in the presence of ATP or UDP further increased channel activity which was blocked by glibenclamide.
- 5. The LK channel inhibited by ATPi is very similar in its conductance and other properties to the KATP channel described in tissues other than smooth muscle, in its conductance and properties the MK channel resembles the KNDP channel we have previous described as present in other smooth muscles and opening in responses to KCOs.