Coexistence of two classes of glibenclamide-inhibitable ATP-regulated K+ channels in avian skeletal muscle.
Avian skeletal muscle expresses two types of ATP-sensitive K+ channels which have a unitary conductance of 15pS. These K+ channels can be distinguished pharmacologically by their high or low sensitivity to the antidiabetic sulphonylurea blocker glibenclamide. Both channels are activated by the K+ channel opener cromakalim. Chick skeletal muscle expresses high-affinity binding sites for [3H]glibenclamide (Kd = 0.6nM) which presumably correspond to the ATP-sensitive K+ channels with the greatest sensitivity to glibenclamide. The density of these high-affinity binding sites varies during muscle development. The maximum density (500fmol/mg protein) appears at 16 days in ovo, i.e. at a period when myoblasts have differentiated into myotubes and when innervation of myotubes has started. After this maximum, the level of [3H]glibenclamide-binding sites decreases to a plateau value of 100fmol/mg protein at 2-5 days post-natal. When muscle cells are put in cultures, the high-affinity binding sites disappear rapidly. Neither glibenclamide nor cromakalim have any effect on normal physiological chick muscle contraction. They have no effect on contracture and/or 86Rb+ efflux produced by metabolic poisoning.
Fosset
M
M
Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des Lucioles, Sophia Antipolis, F-06560 Valbonne, France.
Allard
B
B
Lazdunski
M
M
D000255:Adenosine Triphosphate / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D004594:Electrophysiology; D005905:Glyburide / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism*; D012414:Rubidium Radioisotopes
D015221:Potassium Channels; D012414:Rubidium Radioisotopes; D000255:Adenosine Triphosphate; D005905:Glyburide