Abstract
A quantitative analysis of CO 2 transport and excretion was conducted in seawater acclimated rainbow trout ( Oncorhynchus mykiss) swimming at different sustained swimming velocities. CO 2 excretion increased linearly with cardiac output during exercise but arterial P CO 2 (Pa CO 2 ) and total CO 2 levels also increased indicating a diffusion limitation to CO 2 excretion. The elevated Pa CO 2 was not accompanied by a decrease in pH, indicating that the acid–base compensation was rapid. Mixed-venous P CO 2 increased to a greater extent than Pa CO 2 resulting in a large increase in the venous–arterial difference in P CO 2 (Pv CO 2 −Pa CO 2 ). The Pv CO 2 −Pa CO 2 difference was used to calculate the proportion of total CO 2 excreted comprised of dissolved CO 2 which accounted for less than 1% of total CO 2 excreted in fish swimming at 11 cm sec −1 but increased to about 9% at the greatest swimming velocity indicating that the pattern of CO 2 excretion changes during exercise. There was no effect of exercise on the proportion of CO 2 excreted which was dependent upon HCO 3 −/Cl − exchange (54%) or that which was dependent upon the dehydration of HCO 3 − that resided within the red cell prior to gill blood entry (42%). The large proportion of total CO 2 excreted that was dependent upon HCO 3 −/Cl − exchange is significant because this is thought to be the rate limiting step in CO 2 excretion.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
