Membrane traffic and XXXX release during osmo- and volume regulation in isolated rat renal inner medullary collecting duct cells.

@entity5121 @entity10751 @entity2822 @entity2823 @entity2421 @entity1360 @entity460
In response to @entity2421 stress, cells of the inner medullary collecting duct (IMCD) undergo swelling followed by a regulatory volume decrease (RVD) and a transient release of organic osmolytes such as @entity5121 . In this study, we tested the hypothesis whether membrane recycling is involved in the latter process. Therefore, the state of submembranal actin and the cellular uptake or release of the fluid-phase marker @entity2822 ( @entity2823 )-dextran ( @entity10751 ) were investigated as related to changes in membrane permeability for @entity5121 . After exposure to @entity2421 medium the submembranal actin web rapidly disaggregated but it started to reorganize after 5 min of incubation. The basal-lateral pole of IMCD cells showed a significant uptake of extracellular @entity10751 after 100 sec. After 5 min, part of this fluorescence intensity had moved towards the cell center but the main part remained submembranal. Disintegration of the actin network by cytochalasin D diminished the uptake of @entity10751 during @entity2421 as did a permanent increase in intracellular @entity460 induced by @entity1360 treatment. During a second osmotic stimulation of IMCD cells preloaded with @entity10751 , @entity10751 was released in a linear time course reaching a plateau after 1 min. Isotonic @entity1360 treatment of preloaded cells also generated a rapid @entity10751 release during the first minute but induced a further 2-fold increase during the next 4 min. Under both conditions initial @entity10751 release was highly correlated with the simultaneously determined increase in @entity5121 permeability. A similar strong correlation was found when different incubation temperatures were used (0 degree C, 15 degrees C, 37 degrees C). These results suggest that during exposure of IMCD cells to @entity2421 the submembranal actin web rapidly disintegrates, and "reserve" vesicles, probably containing @entity5121 transporter, move to and fuse with the basal-lateral plasma membrane. The fusion causes a rapid increase in @entity5121 permeability. These membrane areas are recovered by internalization, and the transport systems for @entity5121 are concomitantly retrieved. In parallel to this internalization the submembranal actin filament network is rearranged. This process seems to be regulated by changes in intracellular @entity460 .
