Effects of nitrite-induced methaemoglobinaemia on oxygen affinity of carp blood |
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| Authors: | E Mark Williams Mogens L Glass Norbert Heisler |
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| Institution: | (1) Abteilung Physiologie, Max-Planck Institut für experimentelle Medizin, D-3400 Göttingen, Germany;(2) Department of Physiology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, 14.049 Ribeirão Preto, São Paulo State, Brazil;(3) Present address: Nuffield Department of Anaesthetics, University of Oxford, Radcliffe Infirmary, Oxford, OX2 6HE, UK |
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| Abstract: | Synopsis The oxygen transport characteristics and the acid-base status of carp blood was studied in vitro by equilibration of blood samples with and without addition of 5mmol l–1 of nitrite for 30 min at various Po2 values in combination with Pco2 of 1.5 and 5.7mmHg (0.2 and 0.76kPa). After equilibration pH, Po2, Pco2, and Co2 as well as methaemoglobin and HCO3
– concentration were determined and oxygen dissociation curves established. At Pco2 of 1.5mmHg (0.2kPa) oxygen affinity, expressed by a normal P50 of 3.3mmHg (0.44kPa) was unaffected by nitrite exposure, whereas at Pco2 5.7 (0.76kPa), nitrite exposure shifted P50 from 7.59mmHg (1.01kPa) to 21.9mmHg (2.92kPa). Methaemoglobin formation was greater at the higher Pco2 and increased with falling Po2. Erythrocyte shrinkage and rising plasma HC03
–] during nitrite exposure indicated that the erythrocyte osmoregulation was significantly affected. The present results indicate significantly reduced oxygen affinity upon exposure of carp blood to nitrite. This result contrasts with findings in mammalian blood, where oxygen affinity is greatly enhanced. |
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| Keywords: | Fish Cyprinidae Cyprinus carpio Erythrocyte osmoregulation Oxygen affinity |
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