Proceedings of The Physiological Society

University of Leeds (2008) Proc Physiol Soc 10, PC39

Poster Communications

TRPM8-mediated calcium signals in arterial smooth muscles

L. Borisova1, M. Kustov2, A. Zholos2, T. Burdyga1

1. Physiology, University of Liverpool, Liverpool, United Kingdom. 2. Cardiovascular Biomedical Research Centre, Queen's University Belfast, Belfast, United Kingdom.

Although the cold and menthol receptor (CMR1) TRPM8 channel is now best characterised as the principal sensor of cold stimuli in the peripheral nervous system, TRPM8 is also expressed in prostate, liver and in the vasculature where its functional role is much more elusive. TRPM8 can mediate both Ca2+ influx and Ca2+ release due to its dual (plasma membrane and Ca2+ stores) localisation (Tsuzuki et al., 2004; Zhang & Barritt, 2004; Thebault et al., 2005; Abeele et al., 2006; Bidaux et al., 2007). However, little is known about the functional role of TRPM8 channels, in particular in control of Ca2+ signaling in smooth muscle cells of blood vessels. We have therefore investigated the role of TRPM8 channels in control of Ca2+ signaling in response to menthol using confocal imaging of Fluo-4 loaded isolated cells and in situ vascular myocytes of rat tail artery where expression of TRPM8 channels and their involvement in control of mechanical activity have been shown (see Melanaphy et al at this meeting). A minimum of 7 intact vessels from 7 humanely killed rats were used in the present study. Both in isolated cells and in blood vessels in situ menthol (300µM) produced Ca2+ transients which consisted of an initial “phasic”, followed by a sustained component. The amplitude of the phasic component was 31.7±2.5% and tonic 11.2±1.2% of peak phenylephrine (10 µM) induced Ca2+ transient. The “phasic” component appeared as asynchronous intracellular propagating Ca2+ waves associated with asynchronous mechanical oscillations which integrated into a small contraction of the vessel segment. In Ca2+-free solution containing 2 mM EGTA, the Ca2+ transient induced by menthol consisted of intracellular Ca2+ waves while the sustained component was abolished. Both components of Ca2+ transients induced by menthol were resistant to nifedipine (10 µM), suggesting little role for L-type Ca2+ channels. Ryanodine (50 µM) fully blocked the phasic component of both phenylephrine and menthol induced Ca2+ transients while sustained component induced by both agents was not abolished suggesting an important role of RyRs in the generation of menthol induced Ca2+ waves. We conclude that in SMCs of rat tail artery Ca2+ transient induced by menthol consists of both Ca2+ release and Ca2+ entry components which could contribute to the mechanisms controlling vascular tone in macrovessels.

Where applicable, experiments conform with Society ethical requirements