Muscle KATP channels
Avian muscle contraction
Springer Online Journal Archives 1860-2000
Abstract Avian skeletal muscle expresses two types of ATP-sensitive K+ channels which have a unitary conductance of 15 pS. 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 (K d=0.6 nM) 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 (500 fmol/mg protein) appears at 16 days in ovo, i.e. at a period when myoblasts have di¤erentiated 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 100 fmol/mg protein at 2–5 days postnatal. 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.
Type of Medium: