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Journal of Experimental Biology 133,339-352 (1987)
Published by Company of Biologists 1987

The Regulation of Haemocyanin Oxygen Affinity During Emersion of the Crayfish Austropotamobius Pallipes : III. The Dependence of Ca²⁺-Haemocyanin Binding on the Concentration Of L-Lactate

S. MORRIS ¹, C.R. BRIDGES ¹, and M. K. GRIESHABER ¹

¹ Institut für Zoologie IV, Unversität Düsseldorf, Universitätsstrae 1, D-4000 Düsseldorf, FRG

The binding of Ca²⁺ to the haemocyanin of the crayfish Austropotamobius pallipes was investigated. The amount of bound Ca²⁺ was determined using an ultrafiltration technique to produce haemocyanin-free solutions, the Ca²⁺ concentration of which could then be compared with that of the original, unfiltered solution. Any difference between the two values would indicate the amount of calcium bound by haemocyanin.

The effect of L-lactate on Ca²⁺ binding was investigated by determining the amount of bound ion at different concentrations of L-lactate. In addition, oxygen equilibrium curves were constructed for some of the solutions to verify that the haemocyanin oxygen affinity remained sensitive to L-lactate and to determine whether the haemocyanin was functionally similar to that used in previous investigations.

With 17 mmol 1^-1 total Ca²⁺ and approximately 1 mmol 1^-1 L-lactate the number of Ca²⁺ binding sites was estimated to be between eight and nine per haemocyanin molecule. Without taking into account the formation of calcium lactate, the observed dependency of Ca²⁺-haemocyanin binding on L-lactate concentration could best be described by the equation: Ca²⁺/Hc = 8.64-0.32[lactate^-].

A ‘worst case’ estimate for maximum calcium lactate formation, assuming Ca²⁺ to be the only counterion available to lactate, altered the relationship slightly to: Ca²⁺/Hc = 8.65-0.35[lactate^-].

Note:
Present address: Department of Biological Sciences, University of Calgary, 2500 University Drive N/V, Calgary, Alberta, Canada T2N 1N4.

Key words: crayfish, haemocyanin, lactate, calcium, oxygen affinity

Accepted on June 4, 1987