Modulation of haemocyanin oxygen affinity in the intertidal prawn Palaemon elegans (Rathke)

The modulation of haemocyanin oxygen affinity was studied at 10 degrees C in the blood of the intertidal prawn Palaemon elegans. On increasing the L-lactate concentration in dialysed blood from 0 to 9.1 mM, P50 decreased from 27 to 11 torr at pH 7.8. Undialysed blood exhibited a higher oxygen affinity than dialysed blood with the same lactate concentration indicating the presence of an unidentified factor which increased oxygen affinity. After dialysis both winter and summer blood exhibited the same intrinsic oxygen affinity and response to lactate. The response of oxygen affinity to lactate was exponential, low concentrations of lactate (0-5 mM) markedly increasing oxygen affinity. The lactate effect in dialysed blood expressed as delta logP50/delta log[L-lactate] was -0.56 at pH 7.8 and -0.63 at pH 7.4. The effect of lactate on oxygen affinity, delta P50, was similar in dialysed and whole blood. The effect of the unidentified factor (delta P50, between dialysed and undialysed blood) at the same lactate concentration was 13.1 and 15.1 torr at pH 7.8 in winter and summer blood, respectively. At pH 7.4 the delta P50 was 38 torr for both summer and winter blood. Differences in oxygen affinity between blood collected in summer and winter could be explained by differences in blood lactate concentrations.