Eddinger T J, Murphy R A
Department of Physiology, University of Virginia School of Medicine, Charlottesville 22908.
Arch Biochem Biophys. 1991 Feb 1;284(2):232-7. doi: 10.1016/0003-9861(91)90290-y.
Smooth muscle cells express isoforms of actin and myosin heavy chains (MHC). In early postnatal animals the nonmuscle (NM) actin and MHC isoforms in vascular (aorta) smooth muscle were present in relatively high percentages. More than 30% of the MHC and 40% of the actin isoforms were NM. The relative percentage of the NM isoforms decreased significantly as the animals reached maturity, with NM MHC less than 10% and NM actin less than 30% of the totals. Concurrent with this decrease in NM isoforms was an increase in the smooth muscle (SM) isoforms. The relative changes and time frame in which these changes occurred were very similar for the actin and MHC isoforms. In arterial tissue there were species differences for changes with development in the two SM MHC isoforms (SM1 and SM2). The ratio of SM1:SM2 in young rat aorta was approximately 0.5, while this same ratio was approximately 3 in young swine carotid. Both adult rats and swine had a SM1:SM2 MHC ratio of approximately 1.2. Rat bladder smooth muscle showed no significant change in NM vs SM ratio between young and old rats, while the SM1:SM2 ratio decreased from 2.7 to 1.7 between these age groups. The shifts in alpha and beta actin were similar to those in the vascular tissue, but of much smaller magnitude.
平滑肌细胞表达肌动蛋白和肌球蛋白重链（MHC）的亚型。在出生后早期的动物中，血管（主动脉）平滑肌中的非肌肉（NM）肌动蛋白和MHC亚型所占比例相对较高。超过30%的MHC和40%的肌动蛋白亚型为NM型。随着动物成熟，NM亚型的相对比例显著下降，NM MHC占总量的比例不到10%，NM肌动蛋白占总量的比例不到30%。与NM亚型的这种减少同时发生的是平滑肌（SM）亚型的增加。肌动蛋白和MHC亚型的相对变化及其发生的时间框架非常相似。在动脉组织中，两种SM MHC亚型（SM1和SM2）随发育的变化存在物种差异。幼鼠主动脉中SM1:SM2的比例约为0.5，而幼猪颈动脉中的这一比例约为3。成年大鼠和猪的SM1:SM2 MHC比例均约为1.2。大鼠膀胱平滑肌在幼鼠和成年鼠之间的NM与SM比例没有显著变化，而在这些年龄组之间，SM1:SM2比例从2.7降至1.7。α和β肌动蛋白的变化与血管组织中的变化相似，但幅度要小得多。
