Arginase activity of Bufo arenarum embryos is sensitive to external osmotic pressure.

We investigated the impact of environmental osmotic stress on the arginase activity if Bufo arenarum embryos. The activity at the first developmental stages was not sensitive to extreme variations of osmotic pressure of the environment. Later, at gill circulation, opercular fold and right operculum stages, the enzyme activity of embryos developed in concentrated solutions decreased significantly with respect to control. At complete operculum stage, the arginase activity increased 1.3-2.5 fold in all conditions, and was significantly higher in embryos grown in distilled water than in control animals.