Alterations of molecular architectures in skeletal muscle plasma membranes of dehydrated and water-loaded mice

Abstract

It is likely that orthogonal arrays (OAs) and caveolae seen on the replicas of freeze-fractured muscle plasma membranes are involved in maintaining osmotic homeostasis. Therefore, using the freeze-fracture technique, we examined the ultrastructural changes in OAs and caveolae of the skeletal muscle plasma membrane of dehydrated and water-loaded mice. In the muscle plasma membranes of 6 dehydrated and 6 water-loaded mice, caveolar distribution was not altered, and the densities of caveolae and OAs did not show statistically significant differences when compared with those in 6 control mice, although the skeletal muscles of water-loaded mice sometimes had muscle plasma membranes with extremely numerous OAs. In contrast, the muscle plasma membranes of dehydrated mice often revealed changes in the distribution of OAs, which existed in a group at the confined area of the muscle plasma membranes and were frequently accompanied by the aggregations of intramembranous particles (IMPs) around OAs. Thus, on the basis of the present study, we suggest that OAs in skeletal muscles as well as those in brain may play an important role in maintaining osmotic homeostasis of these organs under abnormal water balance.