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Journal of Experimental Biology 142,125-142 (1989)
Published by Company of Biologists 1989

The Effects of Hypersaline Exposure on Oxygen-Affinity of the Blood of the Freshwater Teleost Catostomus Commersoni

R. L. WALKER ¹, P. R. H. WILKES ², and C. M. WOOD ³

¹ Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4
² Department of Medical Physiology, Health Sciences Centre, University of Calgary, Calgary, Alberta, Canada T2N 1N4
³ Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1

After 10 days' exposure to an environmental salinity of 300 mosmol kg^-1 NaCl, the freshwater stenohaline teleost Catostomus commersoni exhibited an increase in plasma osmolality and a reduction in plasma strong ion difference (SID). There were reductions in plasma pH (pHe), red blood cell (RBC) pH (pHi), plasma total CO₂ and erythrocyte nucleoside triphosphate (NTP) concentration, and increases in mean erythrocyte volume and plasma catecholamine levels. Despite the acidosis, the in vitro haemoglobin oxygen-affinity of blood from saline-acclimated fish was not significantly different from that of control fish (held in fresh water) which had higher pHe and pHi values at the P_CO2 tensions used. In vitro adjustment of SID of blood from control fish to approximate that of the saline-acclimated fish by the addition of NaOH and HCl significantly reduced pHe, pHi and the haemoglobin oxygen-affinity. Adjustment of the plasma osmolality of blood from control fish to values identical to those of the saline-acclimated fish by the addition of NaCl in vitro did not alter the haemoglobin oxygen-affinity. An increase in catecholamine concentration and a decrease in red blood cell NTP concentration in the saline-acclimated fish may have been compensatory mechanisms to maintain haemoglobin oxygen-affinity against acidosis-induced Bohr and Root effects during saline exposure.

Key words: strong ion difference, erythrocyte nucleoside triphosphates, blood oxygen-affinity, Catostomus

Accepted on November 14, 1988