Human atrial and ventricular myosin light-chains subunits in the adult and during development

Abstract

1. Myosin was isolated from human right- and left-atrial and -ventricular myocardium, and examined both in adult subjects and at different stages during pre- and post-natal development. 2. The myosin light-chain subunits in the atria and ventricles were different when characterized by isoelectric focusing and subsequent two-dimensional poly-acrylamide-gel electrophoresis. 3. No differences were observed between the light-chain subunits in the right and left ventricle at any stage of development. 4. The foetal ventricle contained a characteristic light chain that was a major component throughout the latter half of gestation. This foetal light chain, which disappeared in the postnatal period, could not be distinguished from adult atrial light chain 1 on two-dimensional electrophoresis. 5. Myosin in the adult atria, particularly the left, contained components similar to ventricular light-chain components. 6. The possible stimuli for the observed changes in myosin light-chain expression are discussed in relation to the known physiological changes occurring during development.

Two forms of the P light chain of myosin in rabbit and bovine hearts

“…An extra protein, similar in isoelectric point to alkali chain A1, but of smaller Mr, was seen in all foetal and neonatal hearts until ~3 weeks after birth. This protein could represent an embryonic form of light chain A1, similar to that in [25,26] where embryonic forms of light chain A1 were reported in both rat and human hearts.…”

Isolation of cardiac myosin light‐chain isotypes by chromatofocusing

“…Atrial appendages were excised in order to facilitate surgical cardiac by-pass procedures and not for any pathological reasons. Human foetal hearts were obtained as described previously [4]. Subsequent examination post-mortem confirmed the absence of any pathological abnormality in human myocardial specimens.…”

“…In the mammalian foetal ventricle, a foetal light chain (FLC-1) is present which disappears during the early neonatal period to be replaced quantitatively by the adult ventricular light chain (VLC-1) [4]. This foetal light chain has been shown to be similar to the light chain 1 (ALC-1) expressed in the foetal and adult atria [4] and preliminary studies in man have failed to identify Abbreviations. ALC, atrial light chain; VLC, ventricular light chain; FLC, foetal light chain; SDS, sodium dodecyl sulphate.…”

“…Analytical isoelectric focusing of light chains in polyacrylamide gels could be used to predict the results of preparative chromatofocusing for method development. 4. Chromatofocusing was capable of resolving human and bovine cardiac light chain 1 and 2 subunits, atrial (ALC) and ventricular (VLC) light chain isotypes and homologous VLC-2 and VLC-2* light chains.…”

Growth and partial differentiation of presumptive human cardiac myoblasts in culture.

“…Distinct stages in the development of fetal, perinatal, and adult cardiac myocytes can be recognized by morphological (Manasek, 1970;Sreter et al, 1975), biochemical or immunochemical (Hoh et al, 1978;Sartore et al, 1978;Flink et al, 1978;Price et al, 1980;Lompre et al, 1981;Samuel et al, 1983;Lambert et al, 1983;Cummins and Lambert, 1986;Claycomb, 1986), and recently identified molecular (Mahdavi et al, 1982Lompre et al, 1984;Izumo et al, 1985;Nadal-Ginard et al, 1987) criteria. In addition, expression of the major secretory product of the heart, atrial A preliminary account of this work was presented at the UCLA (University of California at Los Angeles) Symposium on the Cellular and Molecular Biology of Muscle Development (Steamboat Springs, Colorado;1988).…”