Observations on “Detubulated” Muscle Fibres

Abstract

GLYCEROL treatment of striated muscle^1–3 has been widely assumed to be a means of disconnecting the transverse tubular system from the surface membrane. Exposure of a sartorius muscle to Ringer plus 400 mM glycerol followed by a return to Ringer, reduces the membrane capacity of superficial fibres, and the muscle is mechanically inactive even though the fibres can transmit action potentials; both these effects might be expected if the transverse tubular system was destroyed or disconnected from the extracellular fluid. We have studied this mechanical decoupling on isolated muscle fibres from the semitendinosus, examining the effects of glycerol concentration. Our results suggest that decoupling may be a complex process and in particular they show that under some circumstances both the depolarization and the loss of the twitch can be reversed by re-exposure to glycerol.