title: Hyperosmolarity-induced stress proteins in chick embryo fibroblasts.
abstract: The effects of a short exposure of chick embryo fibroblasts to a hyperosmolar medium on monovalent cation content, rate of protein synthesis, and polypeptide pattern expression were studied. The hyperosmolar shock gave an immediate and pronounced inhibition of the protein-synthesis rate temporally related to a marked alteration of the intracellular Na+ content. Following the return of the cells to an osmolar environment, the internal Na+ content quickly resumed its previous level, while the recovery of the protein-synthesis rate was more gradual. During the recovery period, there was enhanced expression of at least 12 proteins. The 4 major induced proteins exhibited apparent molecular weights of 96, 87, 70, and 48 kDa. A reduction in the synthesis of five protein bands including three large polypeptides of 220, 160, and 140 kDa was also observed. A comparison with the 3 major proteins induced by a 44 degrees C heat shock indicated an apparent similarity with only two of the hyperosmolarity-inducible polypeptides. Moreover, evidence has been also obtained of the close similarity between the 96 and 75 kDa glucose-regulated proteins and the 96 and 75 kDa proteins inducible by a hyperosmolar shock or by a continuous hyperosmolar treatment, respectively. The kinetics of the stress-proteins appearance indicated nonsimultaneous induction. The presence of actinomycin D during the exposure of the cells to the stress and the recovery period suggested that the expression of some hyperosmolarity-enhanced proteins is regulated at the transcriptional level.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002642:Chick Embryo; D003470:Culture Media / Q000494:pharmacology*; D003609:Dactinomycin / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D006982:Hypertonic Solutions / Q000494:pharmacology*; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism; D014176:Protein Biosynthesis; D011506:Proteins / Q000302:isolation & purification; D012964:Sodium / Q000008:administration & dosage / Q000378:metabolism; D013395:Sucrose / Q000494:pharmacology
chemical_list: D003470:Culture Media; D006982:Hypertonic Solutions; D011506:Proteins; D003609:Dactinomycin; D013395:Sucrose; D012964:Sodium; D005947:Glucose; D011188:Potassium