Segmental Differences in Geometric, Elastic and Contractile Characteristics of Small Intramural Coronary Arteries of the Rat

Abstract

The depedence of elastic and contractile properties on the caliber of small intramural coronary arteries was investigated in the rat in vitro. Different segments of the left anterior descending coronary artery branching system were prepared for microarteriography. The segments were cannulated at both ends, immersed in oxygenated normal Krebs Ringer (nKR) solution. Intraluminal pressure was changed at a rate of about 0.5 mm Hg/s between 0 and 150 mm Hg in repeated cycles. The outer diameter was continuously measured with microangiometry. Pressure-diameter curves were recorded after preconditioning pressure cycles in nKR, with PGF_2α in the bath (7.5 × 10^–6 M), and in maximal relaxation with papaverine (2.8 × 10^–4 M). Biomechanical parameters were computed for vessels grouped according to their calibers (inner diameters: 50–150, 150–250, 250–350, >350 µm). Distensibility and contractility decreased with increasing caliber of the vessels, while the elastic modulus increased. Spontaneous tone was (at 100 mm Hg in mechanically preconditioned vessels) 18.8 ± 4.5, 8.4 ± 4.4, 9.7 ± 3.7 and 8.3 ± 3.8% in the four groups, respectively. PGF_2α contraction was maximal around the 300-µm caliber. Our study is the first direct demonstration that intramural small coronary arteries exhibit characteristic variability in their elastic and contractile properties as a function of their caliber. Such differences may be important in segmentally specific control processes of the coronary microcirculation.

Gender differences in biomechanical properties of intramural coronary resistance arteries of rats, an in vitro microarteriographic study

“…The asterisk indicates isolated statistical significance (po0:05) between the two groups at the given pressure level with the Tukey post-hoc test. toward more peripheral segments of the network (Szekeres et al, 1998). Previously, we also tested biomechanical characteristics of intramural coronary arteries of female rats (Mericli et al, 2004).…”

“…Intramural coronary arteries (approximately and uniformly with 200 mm outer diameter at preparation, end branches of the left anterior descending coronary artery) were isolated as previously described Szekeres et al, 1998). Then a segment with a length of about 2000 mm was cut off and placed in a vessel chamber filled with nKR solution, where it was cannulated at both ends with plastic microcannulas and extended to its in vivo length.…”

“…Description of the microangiometer setup and details of the measuring process were published earlier (Mericli et al, 2004;Nadasy et al, 2001;Szekeres et al, 1998). In brief, a magnified picture of the vessel segment was produced with the aid of a video camera and a monitor (Phillips).…”

“…In addition, direct comparisons of male and female coronary artery functions have been made mostly on large coronary arteries and on subepicardiac arteries (Bowles, 2001;Wellman et al, 1996). It is of utmost importance, however, directly to examine small intramural coronary arteries, as these vessels determine myocardial perfusion, and they may have different myogenic and pharmacological reactivity compared to those of larger subepicardiac vessels (Szekeres et al, 1998). Earlier work from our laboratory has shown that ovariectomy and chronic estrogen replacement induces massive changes in the mechanics of intramural coronary resistance vessels (Mericli et al, 2004).…”

Response of human coronary arteries at different mechanical conditions

“…Studies of the mechanical properties of coronary arteries have been carried out almost exclusively on animals [1]- [9]. Only a few studies [10]- [18] have tried to characterize the in vivo behavior of human coronaries through in vivo and in vitro tests under physiological conditions.…”