Two types of ATP‐sensitive potassium channels in rat portal vein smooth muscle cells
1996; Wiley; Volume: 118; Issue: 1 Linguagem: Inglês
10.1111/j.1476-5381.1996.tb15372.x
ISSN1476-5381
Autores Tópico(s)Cardiac electrophysiology and arrhythmias
Resumo. Single‐channel recordings were made from single, enzymatically isolated smooth muscle cells of rat portal vein by the patch‐clamp technique. . 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. . 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 (K i ) of 11–23 μ m . 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. . 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. . The LK channel inhibited by ATP i is very similar in its conductance and other properties to the K ATP channel described in tissues other than smooth muscle, in its conductance and properties the MK channel resembles the K NDP channel we have previous described as present in other smooth muscles and opening in responses to KCOs.
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