Inhibitory effects of ouabain on early heart development and cardiomyogenesis in the chick embryo

Abstract

Pericardial cavity formation and epithelialization of the cardiac precursor cell population constitute a critical developmental period that precedes stable cardiac cell commitment and differentiation. These events delineate the myocardial and endocardia1 precursor population in the embryo. Restriction of NaK-ATPase (the sodium pump) expression to the pre-cardiomyocyte lateral membranes coincides with these events. NaK-ATPase has been implicated developmentally in cavitation and in maintaining membrane potential. Experiments were undertaken to determine if the effects of perturbing sodium pump activity will affect pericardial cavity formation and, in turn, whether heart formation andor cardiac cell commitment will be affected. We incubated whole chick embryos in vitro between stages 5 to 8 in the presence of the highly specific N d KATPase inhibitor ouabain. Exposure of whole embryos to 10 I.IM ouabain M) demonstrated that heart development and precardiomyocyte differentiation are inhibited principally between stage 5 through stage 7. In each stage the degree of inhibition follows a rostrocaudal gradient as development proceeds along the anterior to posterior axis. After stage 8 ouabain no longer affects heart development or cardiomyogenesis. The inhibition is concentration-and developmental stage-dependent. The inhibition is reversible by elevating the outside potassium ion concentration [KO] in the culture medium or by transferring the embryos into normal medium minus ouabain even after 20 hr of ouabain exposure. The results also suggest that the regulation of the formation of the three-dimensional organ is independent from regulation of myogenesis. 0 1995 Wiley-Liss, Inc.

Sodium‐calcium exchanger (NCX‐1) and calcium modulation: NCX protein expression patterns and regulation of early heart development

“…Our previously published results indicated that ouabain, an inhibitor of the sodium pump, arrested cardiac cell differentiation at a step associated with cardiac cell epithelialization (Linask and Gui, 1995). The sole function of ouabain has been shown experimentally to be an inhibition of Na-K-ATPase (sodium pump) activity.…”

“…Ouabain exposure of whole embryos demonstrated that pericardial coelom development and cardiomyocyte differentiation were blocked principally between stages 4 to 7 in a rostrocaudad gradient. After stage 7 ϩ /8 ouabain no longer affected these cardiac developmental processes (Linask and Gui, 1995). Ouabain inhibition of cardiac cell differentiation suggested that intracellular ionic concentrations may be closely tied to early cardiac signaling and that this may involve also the sodium-calcium exchanger (NCX).…”

“…Previously, we used ouabain, a highly specific Na, K-ATPase inhibitor that has been widely used to inhibit sodium pump activity (Lingrel et al, 1991), to experimentally assess the importance of sodium pump inhibition on the formation of the cardiac compartment and the pericardial cavity (Linask and Gui, 1995). Ouabain exposure of whole embryos demonstrated that pericardial coelom development and cardiomyocyte differentiation were blocked principally between stages 4 to 7 in a rostrocaudad gradient.…”

Early temporal‐specific responses and differential sensitivity to lithium and Wnt‐3A exposure during heart development

“…This process progresses in an anterior to posterior manner across the heart fields (Linask, 2003). The signaling is accompanied by a mesenchymal to epithelial cardiac cell shape change (Linask et al, 1992(Linask et al, , 1997Linask, 1992aLinask, ,b, 2003Linask and Gui, 1995). The mesenchymal to epithelial cell transformation coincides with initiation of cardiomyocyte phenotypic differentiation, i.e., into polarized cells with initiation of myofibrillogenesis (Linask, 1992a;Linask et al, 1997;Imanaka-Yoshida et al, 1998).…”

“…They were removed after a total incubation period of 30 hr and fixed overnight in 4% paraformaldehyde. The in situ hybridization was carried out as previously described (Linask and Gui, 1995). The chick probe for Dkk-1 was provided by Dr. Susan C. Chapman (University of Utah, Salt Lake City, UT).…”