The effect of ethylene glycol and DMSO on fusion of isolated sarcoplasmic reticulum membranes.

Fragmented sarcoplasmic reticulum (FSR) vesicles from rabbit skeletal muscle were suspended in 5-10% ethylene glycol (EG) or in 5, 10, or 15% dimethylsulfoxide (DMSO) and were pelleted onto flat aluminum foil disks. No vesicle fusion o-curs with either 5 or 10% EG treatment and 2-21/2 hours drying. After 4-5 hours drying, 5% EG-treated vesicles have established more areas of close contact and individual vesicles have begun to flatten when compared with the 10% EG vesicles remained round as in the 2-21/2 hour samples of all treatments. Overnight drying also causes extended sheets of bilayer pairs to form in the 5% DMSO-treated samples but, with 10 and 25% treated vesicles, destroys the double bilayers and only occasional dense regions of membrane whorls remain. Both EG and DMSO promote morerapid fusion of FSR vesicles than does glycerol but overnight drying after treatment with 10 or 25% DMSO DESTROYS THE FUSED MEMBRANE.