INCREASE OF C-JUN MESSENGER-RNA UPON HYPOOSMOTIC CELL SWELLING OF RATHEPATOMA-CELLS

c-jun mRNA levels were increased in rat hepatoma cells (H4-II-E-C3) wh en exposed to hypotonic medium (205 mosmol/l) with a maximal induction observed after 1 h of hypotonic exposure. At this time point an appro ximate 5-fold increase in c-jun expression could be detected in relati on to normotonic control incubations (305 mosmol/l). Hypertonic exposu re (405 mosmol/l) had only a slight effect on c-jun expression. In con trast to the increased c-jun mRNA levels under hypotonic conditions, e xpression of the c-fos proto-oncogene was unaffected by changes in the osmolarity. The hypotonicity-induced increase in c-jun expression was also detectable in the presence of a protein kinase C (PKC) inhibitor . This indicates that PKC is not involved in the signal transduction p athway leading to c-jun expression upon hypotonic cell swelling in the se cells.