Actin-like filaments amd membrane rearrangement in oxyntic cells.

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Abstract
The secretory pole of vertebrate oxyntic cells possesses 2 distinct membrane systems: the apical plasma membrane which presents numerous infoldings, microvilli and processes and a complex tubulovesicular system located in close proximity to the plasma membrane. These 2 membrane systems are generally believed to be interconvertible in relation to the functional state of the cell. To determine the role that filaments may play in the interconversion process, the secretory pole of rat and toad [Bufo spinulosus] oxyntic cells was examined by EM under conditions designed to demonstrate filamentous structures, i.e., slight cellular swelling and incubation with heavy meromyosin. Filaments 50-80 .ANG. in diameter are present in close association with the plasma membrane to which they are connected by regularly spaced bridges. Heavy meromyosin-treated material reveals decorated filaments in topographically corresponding locations. No filaments are seen in association with membranes of the tubulovesicular system. Association with actin-like filaments may be a step in the translocation of membranes from the tubulovesicular system to the plasma membrane.