Hypoxic Acclimation in the Lamprey, Lampetra Fluviatilis: Organismic and Erythrocytic Responses

Acute exposure of Lampetra fluviatilis to hypoxia (PO2 = 40–50 mmHg) resulted in a large increase in ventilation frequency and a significant increase in O2 consumption (from 40 to 60 mg kg−1h−1 at 8°C). After 1 week's hypoxia, the O2 consumption decreased (from 60 to 50 mg kg−1 h−1), indicating the existence of slow, acclimatory changes that remove some of the strain from the ventilatory response. The hypoxic animals had a higher blood O2 affinity than the normoxic controls. This acclimatory response is not the result of a decreased allosteric interaction between the haemoglobin and erythrocytic organic phosphates, as in teleost fish, but is attributable partly to dilution of haemoglobin within the red cells and partly to an increase in the intracellular pH. The intraerythrocytic pH of hypoxic animals, measured with a freeze-thaw method, was higher than the plasma pH, suggesting that protons are not passively distributed.