MacKenna D A, Omens J H, Covell J W
Department of Medicine (Cardiology), University of California, San Diego, La Jolla 92093-0613J, USA.
Basic Res Cardiol. 1996 Mar-Apr;91(2):111-22. doi: 10.1007/BF00799683.
The collagen fibers in the myocardium are initially wavy, suggesting that they may not be directly stretched for a portion of diastolic filling. To test whether the fibers gradually straighten and at what left ventricular (LV) pressure they become straight, 24 isolated, arrested rat hearts were fixed at physiologic diastolic LV pressures and changes in collagen structure were examined. As LV pressure increased, mean ( +/- SE) sarcomere length increased (1.80 +/- 0.02 to 1.88 +/- 0.02 from 0 mmHg to 26.3 +/- 4.1 mmHg) while the tortuosity of the perimysial fibers (fiber length/midline length) decreased (1.088 +/- 0.014 to 1.031 +/- 0.006 from 0 mmHg to 26.3 +/- 4.1 mmHg). Transmural variations in collagen structure paralleled the trends in sarcomere length (epicardial regions had longer sarcomeres and straighter collagen fibers than endocardial regions). These results indicate that there is a tight coupling between perimysial collagen fibers and myocytes, consistent with the nonlinear pressure-volume and pressure-sarcomere length relationships.
心肌中的胶原纤维最初是波浪状的，这表明在舒张期充盈的一部分过程中它们可能不会被直接拉伸。为了测试这些纤维是否会逐渐变直以及在何种左心室（LV）压力下它们会变直，将24个离体、停跳的大鼠心脏固定在生理舒张期LV压力下，并检查胶原结构的变化。随着LV压力增加，平均（±标准误）肌节长度增加（从0 mmHg时的1.80±0.02增加到26.3±4.1 mmHg时的1.88±0.02），而肌束膜纤维的曲折度（纤维长度/中线长度）降低（从0 mmHg时的1.088±0.014降低到26.3±4.1 mmHg时的1.031±0.006）。胶原结构的透壁变化与肌节长度的趋势平行（心外膜区域的肌节更长，胶原纤维比心内膜区域更直）。这些结果表明，肌束膜胶原纤维与心肌细胞之间存在紧密耦合，这与非线性压力-容积和压力-肌节长度关系一致。
