Localization of the intracellular site of action of caffeine on skeletal muscle

Abstract

• 1.

  1. Exposure of frog and crayfish skeletal muscle to 10 mM caffeine saline results in a rapid dilation of the sarcoplasmic reticular tubules.

• 2.

  2. Prolonged exposure to caffeine leads to disintegration of the sarcoplasmic reticular membranes, and after 30 min treatment the transverse tubules rupture,' destroying the trids and dyads.

• 3.

  3. Destruction of triads and dyads releases their bound calcium, causing protracted contractures, and the calcium pump of the sarcoplasmic reticulum is inactivated.

• 4.

  4. Tension changes in muscles exposed to caffeine closely parallel the damage caused by caffeine to the sub-cellular structures involved in excitation-contraction] coupling.