Determinants of the contractile properties in the embryonic chicken gizzard and aorta.
Determinants of the contractile properties in the embryonic chicken gizzard and aorta.
复制标题
胚胎鸡砂囊和主动脉收缩特性的决定因素。
DOI：
10.1152/ajpcell.2000.279.6.c1722
复制
发表时间：
2000
期刊：
影响因子：
--
通讯作者：
Brozovich,FV
中科院分区：
文献类型：
--
作者：
Ogut,O;Brozovich,FV
Smooth muscle is generally grouped into two classes of differing contractile properties. Tonic smooth muscles show slow rates of force activation and relaxation and slow speeds of shortening (Vmax) but force maintenance, whereas phasic smooth muscles show poor force maintenance but have fastVmaxand rapid rates of force activation and relaxation. We characterized the development of gizzard and aortic smooth muscle in embryonic chicks to identify the cellular determinants that define phasic (gizzard) and tonic (aortic) contractile properties. Early during development, tonic contractile properties are the default for both tissues. The gizzard develops phasic contractile properties betweenembryonic days(ED)12and20, characterized primarily by rapid rates of force activation and relaxation compared with the aorta. The rapid rate of force activation correlates with expression of the acidic isoform of the 17-kDa essential myosin light chain (MLC17a). Previous data from in vitro motility assays (Rover AS, Frezon Y, and Trybus KM.J Muscle Res Cell Motil18: 103–110, 1997) have postulated that myosin heavy chain (MHC) isoform expression is a determinant forVmaxin intact tissues. In the current study, differences inVmaxdid not correlate with previously published differences in MHC or MLC17aisoforms. Rather,Vmaxwas increased with thiophosphorylation of the 20-kDa regulatory myosin light chain (MLC20) in the gizzard, suggesting that a significant internal load exists. Furthermore,Vmaxin the gizzard increased during postnatal development without changes in MHC or MLC17isoforms. Although the rate of MLC20phosphorylation was similar atED 20, the rate of MLC20dephosphorylation was significantly higher in the gizzard versus the aorta, correlating with expression of the M130 isoform of the myosin binding subunit in the myosin light chain phosphatase (MLCP) holoenzyme. These results indicate that unique MLCP and MLC17isoform expression marks the phasic contractile phenotype.
