The Determination of Optimal Initial Tension in Rat Coronary Artery Using Wire Myography

Abstract

The aim of the present study was to determine the optimal initial tension, i.e. initial stretch for rat coronary artery when using the multi-wire myograph system. We used the normalization procedure to mimic physiological conditions and to stretch the coronary arterial segments to normalized internal circumference (IC1). It is determined the internal circumference when the vessel relaxed under a transmural pressure of 100 mm Hg (IC100), and the IC1 is calculated by multiplying the IC100 by a factor k. The impact of different factor k on the initial stretch and agonist-induced tension of coronary arteries were investigated. The results showed that the maximal agonist-induced tension was achieved at the factor k value of 0.90 and the initial stretch tension was given 1.16±0.04 mN/mm. The most appropriate factor k value was 0.90-0.95 and the most appropriate initial tension was 1.16-1.52 mN/mm. The equilibration time of the coronary artery segments should be at least 1.0 h. In the same optimal initial tension, the agonist-induced tension increased as equilibration time lengthened.

Guidelines for the measurement of vascular function and structure in isolated arteries and veins

“…Therefore, the optimal lumen diameter can be set by adjusting the micrometer position to the IC1 in which the IC100 is corrected (multiplied) by a normalization factor. The normalization factor (also known as the IC1/ IC100 ratio or factor k) for commonly studied arteries from rats are indicated in Table 5 (84)(85)(86)(87). If you are studying a novel vessel with an unknown normalization factor, we recommend that you experimentally determine this value to optimal results.…”

Determining the Optimal Normalization Factor of Different Target Arteries for ex vivo Vascular Function Experiments: A New Standardized Procedure

“…Passive pre-stretching of vascular rings to an IC with optimal contractile response to vasoactive stimuli (IC 1 ) is critical to standardize experimental conditions in wire myography [16]. Several authors have published values for factor k or optimal initial tension of different species and target arteries [2][3][4][5][6][7][8]12]. However, these values were determined empirically using the in-built normalization tool of the corresponding wire myography machine for the determination of IC 1 without a systematic mathematical approach to calculate factor k for the specific target arteries.…”

“…Measurement of isometric contraction force by wire myography is a widely used method to study the response of isolated arteries to vasoactive agonists or antagonists ex vivo. Arteries from a variety of vascular beds of different species can be isolated for this purpose [1][2][3][4][5][6][7][8]. In order to reproducibly study vascular tone regulation ex vivo, the individual pretension of vessel segments for wire myography critically determines the potential to obtain maximum vascular reactivity without provoking vasomotion (spontaneous oscillatory activity) due to immoderate distension [9][10][11].…”

Optimization of resting tension for wire myography in male rat pulmonary arteries

“…However, different vascular beds necessitate different levels of preconstriction due to the baseline in‐vivo pressure differences for each system. For rat basilar arteries and rat coronary arteries, the optimal initial tensions of the vessel segments for a wire myography experiment were empirically determined to be 1.63 ± 0.01 and 1.16–1.52 mN/mm respectively (Ping et al., 2014; Xiao et al., 2015). Overall, wire myography involving systemic vessels have been optimized and reliably established through empirical and literary conventions (Bridges et al., 2011; Ishida et al., 2019; Mulvany & Aalkjaer, 1990).…”

“…The maximum active tension development is achieved when the vessel segments are stretched to a normalized internal circumference (ICn) that mimics physiological condition with the transmural pressure specified at 100 mmHg (IC100) by a factor of 0.9: (Konja et al., 2019; Ping et al., 2014; Xiao et al., 2015). $$$$ IC n=0.9\cdotp IC100 $$$$…”