This Article Full Text Full Text (PDF) All Versions of this Article: biophysj.108.131136v1 95/6/2728    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Koenigsberger, M. Articles by Meister, J.-J. PubMed PubMed Citation Articles by Koenigsberger, M. Articles by Meister, J.-J.

Calcium Dynamics and Vasomotion in Arteries Subject to Isometric, Isobaric, and Isotonic Conditions

Michèle Koenigsberger ^*, Roger Sauser ^*, Dominique Seppey ^*, Jean-Louis Bény  and Jean-Jacques Meister ^*

^* Ecole Polytechnique Fédérale de Lausanne, Laboratory of Cell Biophysics, Lausanne, Switzerland; and Department of Zoology and Animal Biology, University of Geneva, Geneva, Switzerland

Correspondence: Address reprint requests to Michèle Koenigsberger, Tel.: 41-21-693-8347; E-mail: michele.koenigsberger{at}epfl.ch.

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.