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

Abstract

ABSTRACT A spontaneously ventilating, blood-perfused trout preparation is described and its suitability for the study of gas exchange in fish assessed. Cardiovascular dynamics closely approximated those found in vivo; perfusion flow rate .100 g−1, ventral aortic pressure (VAP) = 58·8 cm H2O, dorsal aortic pressure (DAP) = 34·8 cm H2O. 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 . Min−1.100 g−1) and carbon dioxide excretion rates . Min−1.100 g−1) acro the gills. Across the systemic circulation, oxygen was extracted .min−1.100 g−1) and carbon dioxide produced by the metabolizing tissue (.min−1, 100 g−1). The respiratory quotient (REJ 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 (RQs) was 0·83, a more reasonable value. Breathing rate (fg) was maintained at 69·4 ventilations. Min−1. The mean vascular resistance of blood-perfused gills (Rg) was 14·2 cm H2O.ml−1.min. 100 g−1, a value higher than that usually measured in vivo. Mean systemic vascular resistance (Rs) was 19·2 cm H2O. ml−1. min. 100 g−1 which is similar to that measured in intact fish. Cardiovascular responses to hypoxia and adrenergic responses in the branchial and systemic circulations of these preparations also closely approximated those found in vivo. 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.