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Respiratory adaptations in carp blood. Influences of hypoxia, red cell organic phosphates, divalent cations and CO2 on hemoglobin-oxygen affinity

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This study concerns the adaptation of oxygen transporting function of carp blood to environment hypoxia, tracing the roles played by erythrocytic cofactors, inorganic cations, carbon dioxide and hemoglobin multiplicity. Carp acclimated to hypoxia ( 30 mmHg) display striking increases in blood oxygen affinity compared to normoxic ( =120-150 mm) specimens (P 50's are 3.0 and 7.0 mm, respectively, at pH 7.9 and 20øC). This correlates with a marked decrease in erythrocytic concentrations of NTP (nucleoside triphosphates) (Figs. 1, 2, Table 1), permitting investigation of the time-course of the response (Fig. 3). That GTP (guanosine triphosphate) plays a greater role than ATP in the allosteric regulation of blood oxygen affinity, follows from greater decreases in its concentration during hypoxia, and its greater effect on oxygen affinity of the hemoglobin (Figs. 1, 5). It is furthermore shown that divalent cations (which complex with NTP) inhibit the regulatory role of GTP on O2 affinity to a lesser extent than that of ATP (Fig. 7). However, the divalent cation, Mg2+, occurs in similarly high concentrations in the erythrocytes of hypoxic and normoxic fish (Table 1). CO2 specifically depresses the O2 affinity of carp hemoglobin, but below pH 8.3, its effect is obliterated by ATP and GTP suggesting that the chains are the main sites for CO 2 - binding. Four carp hemoglobin components are isolated and their oxygen-binding properties compared with those of the cofactor-free hemolysate (Figs. 4, 8, 9). The results are discussed comparatively with special reference to hemoglobin function in fish and mammals.
TidsskriftJournal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology
Sider (fra-til)127-137
Antal sider11
StatusUdgivet - 1978


  • roy, blood, hypoxia, cations, phosphates, vertebrates, respiration, fish, rbc, carbon dioxide, oxygen affinity, hemoglobin, carp, CO2, adaptation, red cell

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