BIOPHYSICAL THEORY AND MODELING |
Calcium dynamics and vasomotion in arteries subject to isometric, isobaric, and isotonic conditions
Michèle Koenigsberger 1*, Roger Sauser 2, Dominique Seppey 2, Jean-Louis Bény 3 and Jean-Jacques Meister 2
1 Ecole Polytechnique Federale de Lausanne (EPFL)
2 Ecole Polytechnique Fédérale Lausanne
3 University of Geneva
* To whom correspondence should be addressed. E-mail: michele.koenigsberger{at}epfl.ch.
Submitted on February 7, 2008
Revised on March 18, 2008
Accepted on 4 June 2008
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Abstract |
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In vitro, different techniques are used to study the smooth muscle cells calcium dynamics and contraction/relaxation mechanisms on arteries. Most experimental studies use either an isometric or an isobaric setup. However in vivo, a blood vessel is neither isobaric nor isometric nor isotonic, as it is continuously submitted to intraluminal pressure variations arising from heart beat. We use a theoretical model of the smooth muscle calcium and arterial radius dynamics to determine whether results may be considerably different depending on the experimental conditions (isometric, isobaric, isotonic, or cyclic pressure variations). We show that isobaric conditions appear to be more realistic than isometric or isotonic situations, as the calcium dynamics is similar under cyclic intraluminal pressure variations (in vivo like situation) and under a constant pressure (isobaric situation). The arterial contraction is less pronounced in isotonic than in isobaric conditions, and the vasoconstrictor sensitivity higher in isometric than isobaric or isotonic conditions, in agreement with experimental observations. Interestingly, the model predicts that isometric conditions may generate artifacts like the coexistence of multiple stable states. We have verified this model prediction experimentally using rat mesenteric arteries mounted on a wire myograph and stimulated with phenylephrine.
Key Words:
calcium oscillations, contraction, mathematical model, smooth muscle cells
