Effects of experimental anemia on the ATP content and the oxygen affinity of the blood in the rainbow trout (Salmo gairdnerii).

Blood oxygenation properties have been investigated in rainbow trout, 1 and 48 hr after an approximately 25% loss of blood. In both cases the hematocrit was nearly halved. The ATP/Hb4 ratio was significantly increased by 35 and 46% after 1 and 48 hr, respectively. The P 1/2 value (at pH 7.7 and 20 degrees C) was significantly raised, by about 2 mmHg, in both cases. After 48 hr, this decrease in the blood-oxygen affinity and the increase in the red-cell ATP content were significantly positively correlated. The mean corpuscular hemoglobin concentration (MCHC) value was never significantly changed. The pH was decreased by about 0.1 unit after 1 hr but normal values were found after 48 hr. It is suggested that these variations might be of adaptative value for fish in conditions of normal environmental pO2.