Response of Chicken Ductus Arteriosus to Hypercarbic and Normocarbic Acidosis

Abstract

Background: Changes in pH can have profound effects on vascular tone and reactivity, but their influence on the ductus arteriosus (DA) remains unknown. Objective: To analyzethe effects of hypercarbic and normocarbic acidosis in the reactivity of the chicken DA. Methods: DA rings from 19-day chicken fetuses (total incubation time, 21 days) were mounted in a wire myograph for isometric tension recording. Results: In DA rings (pulmonary side) stimulated with O₂, norepinephrine (NE), KCl, or U46619, changes from control conditions (5% CO₂, 24 mM NaHCO₃, pH 7.4) to 7.5% CO₂ (pH 7.25) or 10% CO₂ (pH 7.14) induced a concentration-dependent relaxation that reached 43.0% (SD 21.3) of the O₂-, 28.6% (SD 23.1) of the NE-, 10.4% (SD 18.7) of the KCl-, and 6.8% (SD 12.6) of the U46619-induced contraction. Hypercarbic-acidosis-induced relaxation was impaired by the non-selective K⁺ channel blocker tetraethylammonium or the BK_Ca channel inhibitor iberiotoxin. Normocarbic acidosis (5% CO₂, 12 mM NaHCO₃, pH 7.13) induced transient relaxation of the DA, which was not affected by the presence of tetraethylammonium or iberiotoxin. Euhydric hypercarbia (10% CO₂, 48 mM NaHCO₃, pH 7.46) induced a transient contraction of the DA. Conclusions: Our results indicate that the chicken DA is very sensitive to changes in extracellular pH, and that stimulation of BK_Ca channels may account for the ductal-relaxing effects of hypercarbic acidosis.

Vasoactivity of the gasotransmitters hydrogen sulfide and carbon monoxide in the chicken ductus arteriosus

“…After an equilibration period of 30 min, the vessels were distended to a resting tension corresponding to a transmural pressure of 10 mmHg (15-day embryos) or 20 mmHg (19-day and 21-day embryos). These pressures correspond to the mean arterial blood pressure reported in chicken embryos at the corresponding age (6) and elicit the highest contractile response to KCl, as determined in previous experiments (33,46). After 30 min of incubation at basal tone, a control contraction was elicited by raising the K ϩ concentration of the buffer to 62.5 mM (in exchange for Na ϩ ).…”

Developmental changes in mesenteric artery reactivity in embryonic and newly hatched chicks

“…The expression of smooth muscle proteins and myosin heavy chain isoforms have been shown to be developmentally regulated and tissue dependent in mammals (Sakurai et al 1996; Slomp et al 1997). From the different chicken embryo vessels that our group have studied—carotid, femoral, pulmonary, chorioallantoic (CA) arteries, and ductus arteriosus (DA)—only the DA (Agren et al 2007; Flinsenberg et al 2010; Moonen et al 2010b) and the CA arteries (Lindgren et al 2010) showed an early “mature” contractile function at E15 comparable to the one observed in the MA (Fig. 5).…”

“…In the last few years, the chicken embryo has emerged as a suitable model for studying developmental vascular biology (Agren et al 2007, 2008, 2009; Moonen et al 2010b; Rouwet et al 2000; Ruijtenbeek et al 2002; Sutendra and Michelakis 2007; Villamor et al 2002; Zoer et al 2009, Zoer et al 2010a, b). In contrast to mammals, which depend on a continuous transference of nutrients from the maternal circulation to the developing fetus, all the nutrients required for the formation and growth of the chicken embryo are pre-packaged in the egg at the time of laying (Speake et al 1998).…”

Type I and II Pneumocyte Differentiation in the Developing Fetal Chicken Lung: Conservation of Pivotal Proteins from Birds to Human in the Struggle for Life at Birth

“…Its utility has been greatly extended during the last decade with the development of a variety of manipulation techniques [3,4,5]. Fundamental differences and advantages relative to mammals make the chicken embryo a complementary and valuable model for studies of lung function.…”