Age-related increases in diaphragmatic maximal shortening velocity.
Age-related increases in diaphragmatic maximal shortening velocity.
复制标题
膈肌最大缩短速度与年龄相关。
DOI：
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发表时间：
1996
影响因子：
3.3
通讯作者：
S. Dodd
中科院分区：
文献类型：
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作者：
S. Powers;D. Criswell;R. A. Herb;H. Demirel;S. Dodd
最近的证据表明，老化的结果在增加快速（IIB型）肌球蛋白重链（MHC）在大鼠膈肌。尚不清楚快速MHC的这种年龄相关性变化是否会影响血管最大缩短速度（Vmax）。因此，我们检验了以下假设：衰老与血管Vmax的增加相关，并且Vmax的增加与IIb型MHC的百分比高度相关。用从年轻（4月龄; n = 8）和（年老24月龄; n = 8）雄性Fischer-344大鼠获得的肋隔膜条测量体外收缩特性。与年轻动物相比，老年动物的膈肌最大强直比力产生低14.5%（23.0 +/- 0.4 vs. 19.7 +/- 0.8 N/cm 2; P < 0.05）。相比之下，老年动物的血流Vmax显著高于年轻动物（5.5 +/- 0.1 vs. 4.4 +/- 0.3长度/s; P < 0.05）。尽管老年组的IIb型MHC百分比显著高于年轻组（约+14%; P < 0.05），但Vmax与IIb型MHC百分比之间的相关性相对较低（r = 0.50; P > 0.05）。这些数据支持这一假设，年龄相关的增加，血管Vmax发生，然而，除了IIb型MHC的因素参与调节血管Vmax。有趣的是，尽管衰老导致肌肉最大比力产生减少，但由于肌肉缩短速度增加，老年动物在所有肌肉负荷下的功率输出均得以维持。
Recent evidence demonstrates that aging results in an increase in fast (type IIB) myosin heavy chain (MHC) in the rat diaphragm. It is unknown whether this age-related change in fast MHC influences the diaphragmatic maximal shortening velocity (Vmax). Therefore, we tested the hypothesis that aging is associated with an increase in the diaphragmatic Vmax and that the increase in the Vmax is highly correlated with the percentage of type IIb MHC. In vitro contractile properties were measured with costal diaphragm strips obtained from young (4 mo old; n = 8) and (old 24 mo old; n = 8) male Fischer-344 rats. Diaphragmatic maximal tetanic specific force production was 14.5% lower in the old compared with the young animals (23.0 +/- 0.4 vs. 19.7 +/- 0.8 N/cm2; P < 0.05). In contrast, the diaphragmatic Vmax was significantly higher in the old compared with the young animals (5.5 +/- 0.1 vs. 4.4 +/- 0.3 lengths/s; P < 0.05). Although the percent type IIb MHC was significantly higher (approximately +14%; P < 0.05) in the old compared with the young animals, the correlation between Vmax and percent type IIb MHC was relatively low (r = 0.50; P > 0.05). These data support the hypothesis that an age-related increase in diaphragmatic Vmax occurs; however, factors in addition to type IIb MHC are involved in regulating diaphragmatic Vmax. Interestingly, although aging resulted in a decrease in diaphragmatic maximal specific force production, power output at all muscle loads was maintained in the old animals due to the increase in diaphragmatic shortening velocity.