Oxygenational properties and phosphorylated metabolic intermediates in blood and erythrocytes of the dogfish, Squalus acanthias.

A typical whole blood O2-equilibrium curve from Squalus acanthias had a P50 of 13.2 mmHg and was slightly sigmoidal, having an n value of 1.6 at 15 degrees C, PCO2 = 2.2 mmHg (pH = 7.85). A small Bohr effect was present (phi = -0.28) together with a weak Haldane effect and no Root shift. The predominant trinucleotide, determined by thin layer chromatography, was ATP (0.44 +/- 0.13 S.D. mmol 1(-1) blood) with smaller amounts of GTP present (0.07 +/- 0.02) S.D. mmol 1(-1). Total nucleotide concentrations, determined enzymatically, were low by comparison with teleosts. Incubation of erythrocytes with or without oxygen, or in the presence of a metabolite-enriched 'cocktail' showed limited potential for phosphate cofactor regulation of blood oxygen affinity.