Hyperosmotic modulation of the cytosolic XXXX concentration in a rat osteoblast-like cell line.

@entity11329 @entity7236 @entity2426 @entity3281 @entity1855 @entity15311 @entity4527 @entity593 @entity969 @entity3988 @entity3411 @entity460 @entity594 @entity141
1. The effects of hyperosmotic stress on cytosolic @entity460 concentration ([ @entity141 ]i) were studied by ratio image analysis in single cells of an osteoblast-like bone cell line (RCJ 1.20) loaded with @entity593 AM. 2. The ratio (340 nm/380 nm) of steady-state [ @entity141 ]i in resting osteoblasts kept in Hepes-buffered medium was 0.82 +/- 0.04. A hyperosmotic stimulus (200 mosmol l-1 @entity969 ) produced a [ @entity141 ]i transient with a peak ratio of 1.28 +/- 0.09, which decayed with an apparent half-life (t1/2) of 42.7 +/- 2.6 s. 3. The hyperosmotically induced [ @entity141 ]i transients were insensitive to @entity1855 , @entity3988 or @entity594 , which excludes the involvement of @entity7236 -sensitive @entity141 channels in the process. Non-specific @entity141 channel blockers ( @entity3281 , @entity3411 , @entity11329 or @entity15311 ) partially abolished the hyperosmotically induced [ @entity141 ]i elevation, indicating the contribution of extracellular @entity141 influx. 4. A hyperosmotic stimulus applied in @entity141 -free medium (0.5 mM @entity4527 ) lowered the [ @entity141 ]i peak to a ratio of 0.96 +/- 0.08 (P < 0.001) compared with a @entity141 -containing medium. This suggests that the [ @entity141 ]i increase is due to extracellular influx, as well as release from an intracellular @entity141 pool. 5. Application of @entity2426 (0.5 microM), a specific inhibitor of endoplasmic reticulum @entity141 -ATPase, in @entity141 -free medium caused transient [ @entity141 ]i elevation to peak ratios of 1.33 +/- 0.09, and completely abolished the [ @entity141 ]i response to a hyperosmotic stimulus. This implies the existence of a @entity2426 -sensitive intracellular pool of @entity141 that is mobilized by hyperosmotic stimulus.(ABSTRACT TRUNCATED AT 250 WORDS)
