Kim S J, Iizuka K, Kelly R A, Geng Y J, Bishop S P, Yang G, Kudej A, McConnell B K, Seidman C E, Seidman J G, Vatner S F
Cardiovascular and Pulmonary Research Institute, Allegheny University of the Health Sciences, Pittsburgh, Pennsylvania 15212, USA.
Am J Physiol. 1999 May;276(5):H1780-7. doi: 10.1152/ajpheart.1999.276.5.H1780.
Left Ventricular (LV) myocytes were isolated from 15-wk-old male mice bearing the Arg403 --> Gln alpha-cardiac myosin heavy chain missense mutation (alpha-MHC403/+), a model of familial hypertrophic cardiomyopathy. LV myocytes were classified morphologically: type I, rod shaped with parallel myofibrils; type II, irregularly shaped, shorter and wider than wild-type (WT) control cells, with parallel myofibrils; and type III, irregularly shaped with disoriented myofibrils. Compared with WT myocytes, alpha-MHC403/+ myocytes had fewer type I cells (WT = 74 +/- 3%, alpha-MHC403/+ = 41 +/- 4%, P < 0.01) and more type III cells (WT= 12 +/- 3%, alpha-MHC403/+ = 49 +/- 7%, P < 0.01). In situ histology also demonstrated marked myofibrillar disarray in the alpha-MHC403/+ hearts. With the use of video edge detection, myocytes were paced at 1 Hz (37 degrees C) to determine the effects of the mutation on myocyte function. End-diastolic length was reduced in mutant myocytes, but fractional shortening (% contraction) and sarcomere length were not. Velocity of contraction (-dL/dtmax) was depressed in mutant cells, but more in type II and III cells (-31%) than in type I cells (-18%). Velocity of relaxation (+dL/dt) was also depressed more in type II and III cells (-38%) than in type I cells (-16%). Using fura 2 dye with intracellular Ca2+ transients, we demonstrated that in alpha-MHC403/+ myocytes, the amplitude of the Ca2+ signal during contraction was unchanged but that the time required for decay of the signal to decrease 70% from its maximum was delayed significantly (WT = 159 +/- 8 ms; alpha-MHC403/+ = 217 +/- 14 ms, P < 0.01). Sarco(endo)plasmic reticulum Ca2+-ATPase mRNA levels in alpha-MHC403/+ and WT mice were similar. These data indicate that the altered cardiac dysfunction of alpha-MHC403/+ myocytes is directly due to defective myocyte function rather than to secondary changes in global cardiac function and/or loading conditions.
从携带精氨酸403→谷氨酰胺α-心肌肌球蛋白重链错义突变（α-MHC403/+）的15周龄雄性小鼠中分离出左心室（LV）心肌细胞，该小鼠是家族性肥厚型心肌病的模型。LV心肌细胞按形态学分类：I型，呈杆状，肌原纤维平行排列；II型，形状不规则，比野生型（WT）对照细胞短且宽，肌原纤维平行排列；III型，形状不规则，肌原纤维排列紊乱。与WT心肌细胞相比，α-MHC403/+心肌细胞的I型细胞较少（WT = 74±3%，α-MHC403/+ = 41±4%，P < 0.01），III型细胞较多（WT = 12±3%，α-MHC403/+ = 49±7%，P < 0.01）。原位组织学也显示α-MHC403/+心脏中存在明显的肌原纤维排列紊乱。使用视频边缘检测技术，在37℃下以1Hz的频率对心肌细胞进行起搏，以确定该突变对心肌细胞功能的影响。突变型心肌细胞的舒张末期长度缩短，但缩短分数（%收缩）和肌节长度未改变。突变型细胞的收缩速度（-dL/dtmax）降低，但II型和III型细胞（-31%）比I型细胞（-18%）降低得更多。II型和III型细胞的舒张速度（+dL/dt）也比I型细胞（-16%）降低得更多（-38%）。使用fura 2染料检测细胞内Ca2+瞬变，我们发现，在α-MHC403/+心肌细胞中，收缩期间Ca2+信号的幅度未改变，但信号从最大值衰减70%所需的时间显著延迟（WT = 159±8ms；α-MHC403/+ = 217±14ms，P < 0.01）。α-MHC403/+和WT小鼠的肌浆网Ca2+-ATPase mRNA水平相似。这些数据表明，α-MHC403/+心肌细胞心脏功能障碍的改变直接归因于心肌细胞功能缺陷，而非整体心脏功能和/或负荷条件的继发性变化。
