抄録
Marine organisms including fish (vertebrate) and shellfish (invertebrate) adapt to changes in the osmolality at the cellular level. Fish can maintain the osmolality of body fluid within a certain range due to the highly developed endocrinological system, while shellfish cannot regulate the osmolality of body fluid due to the lack of it. This suggests that shellfish cells are more resistant against osmotic change than fish cells. To compare the osmo-responsive system of fish and shellfish at cellular level, we focussed on the amino acid transporters and examined the expression patterns of their mRNAs following the osmotic change. When examined the expression patterns of fish taurine transporter mRNA following the osmotic change by using EPC cells, cultured carp epidermal cells, specific induction by hyper-osmotic stress was observed. Hyper-osmolality induced expression was also observed in tilapia tissues when tilapia acclimatized to fresh water was immediately exposed to 70% seawater. In contrast to fish, mRNA of oyster amino acid transporter was induced both by hyper- and hypo-osmotic stresses. Unexpected induction of oyster transporter mRNA by hypo-osmotic stress suggests a difference in the promoter function of the transporter genes between fish and shellfish.
