Glycerol treatment in mammalian skeletal muscle.

(1) The effects of glycerol-treatment on the ultrastructure, tension, and electrical properties of rat sternomastoid muscle fibers are described. (2) The effect upon the ultrastructure of fibers differed from that previously reported for amphibian fibers, in that the sarcoplasmic reticulum, as well as the T-system, was disrupted. (3) Tension (tension (tetanus and K-contracture) was abolished when preparations were returned to normal Krebs after exposure to a glycerol-Krebs solution (exposure periods were 1 hr in 200--350 mM-glycerol or 10--60 min in 350 mM-glycerol), although fibers had normal resting membrane potentials and action potentials. (4) Fibers treated for 1 hr with 350 mM-glycerol were detubulated when returned to normal Krebs. Specific membrane capacity was reduced and exogenous horseradish peroxidase (HRP) did not penetrate the T-system. (5) Fibers were not detubulated after treatment for 1 hr with 200 to 300 mM-glycerol or after treatment for 10 to 30 min with 350 mM glycerol. Specific membrane capacity and resistance were normal and HRP entered the T-system. (6) Ultrastructural disruption of the triad junction became progressively more extensive with increasing glycerol concentration used and may be responsible for uncoupling.