Distribution of (Na+ + K+)ATPase and sodium channels in skeletal muscle and electroplax

J Neurocytol. 1987 Aug;16(4):511-22. doi: 10.1007/BF01668505.

Abstract

The distributions of (Na+ + K+)ATPase and sodium channels in skeletal muscle fibres and electrocytes were determined by immunofluorescent and immunoelectron microscopic techniques using antibodies against rat and eel (Na+ + K+)ATPase and the eel electric organ sodium channel. The extrajunctional sarcolemma of skeletal muscle was uniformly stained by polyclonal antibodies against (Na+ + K+)ATPase and the sodium channel. The T-tubule system of skeletal muscle was also labelled heavily for both (Na+ + K+)ATPase and the sodium channel. The terminal cisternae of the sarcoplasmic reticulum was stained for (Na+ + K+)ATPase but not sodium channels. At the motor endplate, (Na+ + K+)ATPase-like immunoreactivity was present along the plasmalemma of motor nerve terminals but not along the postsynaptic junctional sarcolemma. Paradoxically, a monoclonal antibody that binds to the alpha form of the catalytic subunit of (Na+ + K+)ATPase from rat hepatocytes and renal tubule cells did not label the enzyme in rat skeletal muscle. In electrocytes, (Na+ + K+)ATPase-like immunoreactivity was concentrated primarily along the plasmalemma and calveolae of the non-innervated face. In contrast, sodium channel-like immunoreactivity was concentrated along the plasmalemma of the innervated face except in the clefts of the postsynaptic membrane. Thus, we conclude that at endplates both the (Na+ + K+)ATPase of rat skeletal muscle and sodium channels of eel electrocytes are not concentrated in the juxtaneuronal postsynaptic membrane. We also interpret the failure of the monoclonal anti-alpha (Na+ + K+)ATPase antibodies to bind to the enzyme in muscle to indicate that the catalytic subunit of skeletal muscle (Na+ + K+)ATPase displays different epitopes than does the alpha subunit of kidney and liver.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Electric Organ / enzymology
  • Electric Organ / metabolism*
  • Electric Organ / ultrastructure
  • Electrophorus / metabolism*
  • Fluorescent Antibody Technique
  • Ion Channels / metabolism*
  • Mice
  • Muscles / enzymology
  • Muscles / metabolism*
  • Muscles / ultrastructure
  • Rats
  • Rats, Inbred Strains
  • Sodium / metabolism*
  • Sodium-Potassium-Exchanging ATPase / metabolism*

Substances

  • Ion Channels
  • Sodium
  • Sodium-Potassium-Exchanging ATPase