Effects of ATP depletion and protein synthesis inhibition on muscle plasma membrane orthogonal arrays.

We studied the effects of perturbations on the orthogonal arrays of 6- to 8-nm intramembranous particles seen in freeze-fractured fast-twitch rat muscle plasma membrane. We found the arrays to be stable in whole muscle in vitro to 8 to 12 h regardless of the presence of glucose, calcium, or supplemental oxygen. Depletion of ATP with 2,4-dinitrophenol or sodium azide led to a marked reduction in array density without a compensatory increase in nonarray particles. Ninety-five percent inhibition of protein synthesis with cycloheximide had no effect on the arrays to 12 h. These results indicate that muscle plasma membrane orthogonal arrays, if protein, are slow-turn-over structures whose degradation is hastened by ATP depletion.