Proceedings of The Physiological Society
University of Cambridge (2008) Proc Physiol Soc 11, PC15
The presence of mechanosensitive channels in the rainbow trout (Oncorhynchus mykiss) heart
S. M. Patrick1, E. White2, H. A. Shiels1
1. The Faculty of Life Sciences, The University of Manchester, Manchester, United Kingdom. 2. Institute of Membrane and Systems Biology, The University of Leeds, Leeds, United Kingdom.
Mechanosensitivity describes the response to mechanical stimulation in cells, this may occur through the activation of mechanosensitive channels (MSCs). MSCs have been studied in microorganisms and shown to act as mechanoelectrical transducers of the forces exerted upon the cell membrane of the microorganism and so allow the cell to respond to mechanical stimuli (Martinac and Kloda, 2003). More recently, studies have found the degree of mechanosensitivity of mammalian cardiac tissue may contribute to electrical instability and arrhythmic disposition of the heart after myocardial infarction (Kamkin et al, 2005). In this study we looked at the physiological effect of stretch upon the ventricular monophasic action potential (MAP) of the isolated whole O.mykiss heart (n=8). A range of filling pressures (1kPa - 4kPa) were used to stretch the heart and in some experiments outflow from the heart was inhibited to induce a large stretch of the myocardium. MAPs were recorded from the surface of the spontaneously beating heart. An increase in filling pressure from 1kPa to 4 kPa shortened the MAP at 25% repolarisation (one way repeated measures ANOVA, P=0.017). Clamping outflow from the heart shortened this further (P=0.001). No significant differences were found in the MAP at 50% repolarisation time with either changes in filling pressure or clamping outflow. Although no significant difference in repolarisation time at 90% was seen with increased filling pressure, significant elongation (P<0.05) was seen when outflow was clamped. These experiments show that the MAP of O. mykiss is altered, due to stretch, in a similar manner to that which has been described in mammals (see, White, 2006) and may indicate the presence of non-selective cation MSCs in the O.mykiss ventricle. To investigate this further, we have cloned the trout variants of both TRPC1, which has been reported to be a store operated Ca2+ MSC, and TREK-1 which has been identified as a twin pore K+ MSC. We will use this information to look at the evolution of these channels and to determine their presence in different tissues from O. mykiss.
Where applicable, experiments conform with Society ethical requirements