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Journal of Experimental Biology 101,17-34 (1982)
Published by Company of Biologists 1982

Gas Transfer in a Spontaneously Ventilating, Blood-Perfused Trout Preparation

PETER S. DAVIE ¹, CHARLES DAXBOECK ², STEVE F. PERRY ³, and DAVID J. RANDALL ³

¹ Department of Zoology, University of British Columbia, Vancouver, B.C., Canada V6T 2A9; Department of Physiology and Anatomy, Massey University, Palmerston North, New Zealand
² Department of Zoology, University of British Columbia, Vancouver, B.C., Canada V6T 2A9; Pacific Gamefish Foundation, P.O. Box 25115, Honolulu, Hawaii 06825
³ Department of Zoology, University of British Columbia, Vancouver, B.C., Canada V6T 2A9

1. A spontaneously ventilating, blood-perfused trout preparation is described and its suitability for the study of gas exchange in fish assessed.

2. Cardiovascular dynamics closely approximated those found in vivo; perfusion flow rate (Q) = 1·62 ml^-1.100 g^-1, ventral aortic pressure (VAP) = 58·8 cm H₂O, dorsal aortic pressure (DAP) = 34·8 cm H₂O.

3. Gas exchange characteristics in the branchial and systemic circulations also were similar to those described for resting, intact rainbow trout. All preparations showed consistent oxygen uptake (M_g,O2, 1·17 µmol. min^-1.100 g^-1) and carbon dioxide excretion rates (M_g,CO2, 2·05 µmol. min^-1.100 g^-1) across the gills. Across the systemic circulation, oxygen was extracted (M_s,O2, 1·97 µmol. min^-1.100 g^-1) and carbon dioxide produced by the metabolizing tissue (M_s,CO2, 1·63 µmol. min^-1.100 g^-1). The respiratory quotient (RE_g) for gas transfer across the gills was 1·85. This high value was a reflection of the fact that much more oxygen than carbon dioxide was added to venous blood in the tonometer. The respiratory quotient for the tissues (RQ_s) was 0·83, a more reasonable value. Breathing rate (f_g) was maintained at 69·4 ventilations.min^-1.

4. The mean vascular resistance of blood-perfused gills (R_g) was 14·2 cm H₂O.ml^-1.min.100 g^-1, a value higher than that usually measured in vivo. Mean systemic vascular resistance (R_s) was 19·2 cm H₂O.ml^-1.min.100 g^-1 which is similar to that measured in intact fish.

5. Cardiovascular responses to hypoxia and adrenergic responses in the branchial and systemic circulations of these preparations also closely approximated those found in vivo.

6. This preparation is deemed suitable for studies of the cardiovascular system as well as gas transfer. The results from these experiments are representative of the in vivo condition in fish.