Effect of pH on interlamellar spacing in rat sciatic myelin

Tissue sections of rat sciatic nerves were incubated at various pH ranges to study the effects of proton titration on myelin fine structure by transmission electron microscopy. It was found that the major dense line of the sheath can open and close reversibly in response to proton titration at a pH range compatible with in vivo conditions. Opened and closed major dense lines coexisted in the sheath, but the number of opened lines increased with increasing pH. There was a pattern of periodicity in the opening of dense lines in that either one, two, or three opened lines alternated with one closed line. The local opening or closing of a dense line, furthermore, was often associated with reciprocal changes in the two adjacent dense lines, highly suggestive of the interaction of electric fields between the myelin membranes. These observations show that energy can be stored within the myelin leaflet.