Induction of mRNAs in response to acclimation of trout cells to different osmolalities

The direct effect of osmolality on growth and mRNA population were investigated in the rainbow trout cell line (RTG-2). These cells can grow in the media of osmolalities ranging from 200 to 600 mosmol kg-1. With two-dimensional electrophoresis, the in vitro translation of poly(A⁺) RNA isolated from these cells showed osmoresponsive changes in the population of translatable mRNAs. Using differential mRNA display polymerase chain reaction, however, we identified inducible cDNA products in hyper-osmotic and hypo-osmotic media as third component of complement, and as homologues of known genes: an atypical protein kinase regulated by the thyrotropin-dependent mitogenic pathway, nucleolin and CHD3. The remaining cDNAs have no significant homology in GenBank. Northern blots demonstrate that their mRNA levels were induced in hyper-osmotic and hypo-osmotic media, but not by other stresses. The expressed proteins of these mRNAs may be involved directly or indirectly in the adaptation of RTG-2 cells to different osmolalities probably through the osmotic signal transduction and adjustment in cellular metabolism to osmotic stress.