Proceedings of The Physiological Society

University of Cambridge (2004) J Physiol 555P, C84


Sarcomere length-tension relationships in single cardiac ventricular myocytes of the rainbow trout (Oncorhynchus mykiss)

Holly A. Shiels and Ed White

School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK

Increased cardiac output in fish is achieved largely by an increase in stroke volume. This is achieved by an increased end-diastolic ventricular volume and a stretch-induced increase in myocardial contractility known as the Frank-Starling mechanism (Farrell & Jones, 1992). Compared to mammalian myocardium, relatively few details of this mechanism are known for fish.

Trout (159 ± 9 g, mean ± S.E.M.) were killed humanely. Single ventricular myocytes were isolated enzymatically then placed in the chamber of an inverted microscope and superfused at 21-22 °C with a physiological saline solution containing 2 mM Ca2+ (pH = 7.8). Carbon fibre transducers were attached towards either end of the myocyte about 100 µm apart, in order to record tension and to apply axial stretch to the longitudinal axis of the myocyte. Stretch was measured as increased sarcomere length (SL) between the fibres (Hongo et al. 1996). Cells were stimulated by external electrodes at 0.5 Hz and contracted auxotonically.

The mean end diastolic SL was (1.84 ± 0.02

Where applicable, experiments conform with Society ethical requirements