The methemoglobin blood level and stability of circulating erythrocytes of the rockfish Scorpaena porcus to osmotic shock under conditions of experimental hypoxia

Under experimental conditions the oxygen content in water was reduced to 1.3-1.4 mg l(-1) (15% of the saturation) and 2.6-2.7 mg l(-1) (30% of the saturation). The rockfish (Scorpaena porcus L.) were kept under these conditions for 90 min. Analysis of samples has shown a decrease of methemoglobin level by 58.2 % (p < 0.001) and an increase of erythrocyte stability to the osmotic shock. The cell lysis occurred at lower concentrations of NaCl. It is concluded that the process of natural oxygenation is one of the causes of the rise of the oxidized pigment concentration in the fish blood. This is due to low efficiency of erythrocytic NADH-diaphorases and is compensated by an increase of activity of enzymes of the cell antioxidant protection system. The latter prevents from development of peroxidation processes and lysis of cells during their circulation despite a comparatively high level of methemoglobin in blood.