Discrimination between fast- and slow-twitch fibres of guinea pig skeletal muscle using the relative surface density of junctional transverse tubule membrane

J Muscle Res Cell Motil. 1988 Oct;9(5):403-14. doi: 10.1007/BF01774067.


The black reaction of Golgi was used to infiltrate transverse (T) tubules in fast-twitch glycolytic (FW), fast-twitch oxidative-glycolytic (FR) and slow-twitch (S) type fibres in muscles of guinea pigs. Non-junctional (fT) and junctional (jT) segments of the T-tubule network are clearly demarcated by this technique. Digitized planimetry and direct measurements were used to determine the proportion of T-tubule network forming junctions with the sarcoplasmic reticulum (%LjT) and to estimate the surface density (surface area per fibre volume) of total and junctional T membrane. From these data, the volume density (number per fibre volume) of junctional feet was calculated. All three types of fibres have approximately equal surface density of T tubules, but the FW and FR fibres have a much higher proportion of jT. The calculated volume density of feet is twice as high in fast-twitch as in slow-twitch fibres.

Publication types

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

MeSH terms

  • Animals
  • Cell Membrane / ultrastructure
  • Female
  • Guinea Pigs
  • Mathematics
  • Muscle Contraction
  • Muscles / cytology*
  • Muscles / physiology
  • Muscles / ultrastructure
  • Neuromuscular Junction / ultrastructure*
  • Sarcomeres / ultrastructure
  • Sarcoplasmic Reticulum / ultrastructure*