EFFECTS OF ANISOSMOTIC CONDITIONS ON THE CYTOSKELETAL ARCHITECTURE OFCULTURED PC12 CELLS

PC12 cells show a classical volume regulatory process when submitted t o hypo-osmotic conditions. The present study examined the effects of s uch osmotic shock on the structural organization of different cytoskel etal elements. Results were obtained by use of different light and ele ctron microscopy techniques combined with immunostaining methods. It a ppeared that the osmotically induced changes in cell volume were conco mitant with important modifications in the organization of the microfi lament network. Microfilaments concentrated in the perinuclear area, l eaving only radial extensions of poorly organized structures in the cy toplasm. The latter were the only actin structures immunologically sta ined in the cytoplasm and seemed to anchor to the plasma membrane. Mea surements of the fluorescence intensity of PC12 cells treated with FIT C-labeled phalloidin indicated a progressive depolymerization, followe d by a repolymerization of F-actin. This occurs in parallel with micro filament reorganization and volume regulatory processes. The appearanc e of microfilament reorganization was a function of both the incubatio n period and the amplitude of the osmolarity changes. During the first minutes of osmotic shock, a decrease was observed in the density and length of microvilli, which normally cover the PC12 cell surfaces, sug gesting an early reorganization of the underlying microfilament networ k. Microtubules and intermediate filament networks were not affected b y the hypo-osmotic conditions. (C) 1994 Wiley-Liss, Inc.