The Regulation of Haemocyanin Oxygen Affinity during Emersion of the Crayfish Austropotamobius Pallipes I. an in Vitro Investigation of the Interactive Effects of Calcium and L-lactate on Oxygen Affinity

The haemolymph of the crayfish Austropotamobius pallipes exhibits a high affinity for oxygen (P50 = 2-7 Torr at pH7-9 and 15°C) and a modest Bohr effect (<p = —0-455). The affinity of haemolymph dialysed against a crayfish Ringer was lower with a P50 value of 6 4 Torr at the same temperature and pH. The oxygen affinity of the dialysed haemolymph can be increased markedly by increased concentrations of L-lactate and to a greater extent by elevated concentrations of calcium ions. In the dialysed preparation, the potentiating effects of L-lactate and Ca on haemocyanin oxygen affinity were found to be interdependent. Elevating the concentration of one of these two ions reduced the effect of the other. The increase in the oxygen affinity of the haemocyanin brought about by elevated Ca and L-lactate was insufficient to account for the difference in affinity between dialysed and nondialysed haemolymph. The mutually agonistic effects of Ca and L-lactate are described both empirically and graphically.