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First published online October 10, 2003

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Effect of coronary perfusion on the basal performance, volume loading and oxygen consumption in the isolated resistance-headed heart of the trout Oncorhynchus mykiss

C. Agnisola^1,*, L. Petersen² and T. Mustafa²

¹ Università degli studi di Napoli `Federico II', Dipartimento di Fisiologia Generale ed Ambientale, via Mezzocannone 8, 80134-Napoli, Italy
² Institute of Biology, Odense University, Campusvej 55, DK-5230, Odense, Denmark

View larger version (20K): [in a new window]   Fig. 1. Scheme of the perfusion apparatus and pressure recording set-up. The heart was working against a resistance, resulting from the combined effects of Ro (= 6 TPa s m-3) and Rc (= 30 TPa s m-3) (i.e. the reciprocal of the sum of the conductances of the aortic tube and the coronary tube); however, as Ro>>Rc, afterload was depending mainly from Ro. The variable resistance Ri allowed us to set input pressure and flow. Input and output reservoirs were set at 7 and 10 cm, respectively, above the level of saline in the perfusion chamber. Pressures from the chamber (1), the atrium (2), and from saline filled tubes placed upstream (3) and downstream (4) of Ro, and downstream Rc (5), were sequentially acquired via a set of computer controlled valves connected with a pressure transducer. Inset: typical pressure trace recorded upstream Ro (3) under basal perfusion conditions.

View larger version (13K): [in a new window]   Fig. 2. Atrial (squares) and ventricular (circles) preload values during 30 min perfusion of the isolated working trout heart under basal conditions, with (+CF, open symbols) and without (-CF, closed symbols) coronary perfusion. At time 0 the atrial preload was set in order to get a cardiac output of about 15 ml min-1 kg-1. Any successive change indicates a self-adjustment of the heart. Two-way ANOVA indicated a significant difference between +CF and -CF data (P<0.01) in both parameters. Repeated-measures one-way ANOVA and Dunnet post-hoc test applied to -CF data indicated a significant increase in both atrial and ventricular preload 5 min after the beginning of perfusion (P<0.05).

View larger version (16K): [in a new window]   Fig. 3. Ventricular performance during 30 min perfusion of the isolated working trout heart under basal conditions, with (+CF, open symbols) and without (-CF, closed symbols) coronary perfusion. (A) Cardiac output (circles) and power output (squares); (B) stroke volume (circles) and stroke work (squares); (C) afterload (circles) and heart rate (squares). Two-way ANOVA indicated a significant difference between +CF and -CF data (P<0.01) for cardiac output and power output only.

View larger version (15K): [in a new window]   Fig. 4. Coronary flow (filled circles), pressure (open circles) and resistance (open squares) during 30 min perfusion of the isolated working trout heart under basal conditions in the +CF group of hearts. One-way ANOVA indicated that these three parameters were not dependent on perfusion time.

View larger version (18K): [in a new window]   Fig. 5. Volume loading of the isolated working trout heart with coronary perfusion included (+CF, open circles) or excluded (-CF, filled circles). Two-way ANOVA indicated a significant effect of both coronary perfusion (P<0.01) and preload (P<0.001) on stroke work. (Inset A) Relationship between coronary flow and preload in the +CF group. One-way ANOVA indicated no-significant effect of preload on coronary flow. (Inset B) Effect of ventricular preload on afterload of the isolated working trout heart with coronary perfusion included (+CF, open circles) or excluded (-CF, filled circles). Repeated-measures one-way ANOVA indicated a significant effect of preload on afterload in both groups. Two-way ANOVA indicated no significant effect of coronary perfusion on afterload.

View larger version (14K): [in a new window]   Fig. 6. Effect of coronary perfusion on (A) oxygen consumption and (B) mechanical efficiency of the isolated working trout heart under basal perfusion conditions and at maximal volume loading. Two-way ANOVA with Bonferroni post-hoc test indicated a significant effect of preload on O2, but no significant difference was observed between +CF and -CF. Efficiency was not affected by either the perfusion conditions or the presence of coronary perfusion.