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Journal of Experimental Biology 101,47-60 (1982)
Published by Company of Biologists 1982

A Comparison of CO₂ Excretion IA Spontaneously Ventilating Blood Perfused Trout Preparation and Salineperfused Gill Preparations: Contribution of the Branchial Epithelium and Red Blood Cell

STEVE F. PERRY ¹, PETER S. DAVIE ¹, ¹, and DAVID J. RANDALL ¹

¹ Department of Zoology, The University of British Columbia, 2354-6270 University Boulevard, Vancouver, B.C., Canada V6T 2A9

A spontaneously ventilating blood-perfused trout preparation and saline perfused gill preparations were utilized to investigate the role of the erythrocyte and branchial epithelium in CO₂ excretion and acid-base regulation.

CO, excretion (M_COCO2) in blood-perfused preparations was positively correlated with haematocrit (Hct), and was abolished completely during plasma-perfusion.

Elevating HCO₃- concentration of input blood from 10 to 25 mM significantly increased M_COCO2. fourfold in blood-perfused preparations as a result of increased entry of H_CO into the red blood cell and not into the gill epithelium. Increased HCO₃- concentration was without effect in totally saline-perfused coho salmon (Onchorynchus kisutch).

The addition of 4-acetamido-4'-wo-thiocyanatostilbene-2, 2 disulfonic acid (SITS; 10^-4 M) to input blood significantly reduced M_CO, and oxygen uptake (M_g,_OO2) in blood-perfused fish due to inhibition of erythrocytic HCO³-exchange.

Unlike blood-perfused preparations, no saline-perfused preparation (isolated holobranchs or totally perfused rainbow trout or coho salmon) displayed measureable CO, excretion at physiological Pco and pH.

Increased input PCOt in both blood-perfused and saline-perfused preparations significantly increased MCOt due to enhanced branchial diffusion of molecular CO₂.

It is concluded that the entry of HCO₃- into the erythrocyte is the rate-limiting step in CO, excretion and that movement of HCO₃- from plasma to gill epithelium cells in no way contributes to overall CO₃ elimination.

Note:

Department of Physiology and Anatomy, Massey University Palmerston North, New Zealand.

Pacific Gamefish Foundation, P.O. Box 25115, Honolulu, Hawaii, U.S.A. 96825

This article has been cited by other articles:

				P. R. Desforges, S. S. Harman, K. M. Gilmour, and S. F. Perry Sensitivity of CO2 excretion to blood flow changes in trout is determined by carbonic anhydrase availability Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2002; 282(2): R501 - R508. [Abstract] [Full Text] [PDF]