Morphological Changes in the Chicken Ductus Arteriosi During Closure at Hatching

Abstract

The chicken embryo has two functioning ductus arteriosi (DA) during development. These blood vessels connect the pulmonary arteries to the descending aorta providing a right-to-left shunt of blood away from the nonrespiring lungs and to the systemic circuit and chorioallanotic membrane. The DA consists of two distinct tissue types along its length, a muscular proximal portion and an elastic distal portion. During hatching, the DA must close for proper separation of systemic and pulmonary circulation. We examined the morphological changes of the chicken DA before, during, and after hatching. Occlusion of the proximal DA began during external pipping and was complete at hatching. Anatomical remodeling began as early as external pipping with fragmentation of the internal elastic lamina and smooth muscle actin appearing in the neointimal zone. By day 2 posthatch, the proximal DA lumen was fully occluded by endothelial cells and smooth muscle actin positive cells. In contrast, the distal DA was not fully occluded by day 2 posthatch. Increases in Po 2 of the blood serves as the main stimulus for closure of the mammalian DA. The responsiveness of the chicken proximal DA to oxygen increased during hatching, peaking during external pipping. This peak correlated with an increase in blood gas Po 2 and the initial occlusion of the vessel. The distal portion remained unresponsive to oxygen throughout hatching. In conclusion, the chicken DA begins to close during external pipping when arterial Po 2 increases and vessel tone is most sensitive to oxygen.

Morphological and Functional Alterations of the Ductus Arteriosus in a Chicken Model of Hypoxia-Induced Fetal Growth Retardation

“…In addition, the impairment of ACh-and SNP-mediated relaxation, which is a characteristic feature of the mature chicken DA (9), was also observed in the hypoxic fetuses. However, other features of the mature chicken DA, such as the enhanced responsiveness to O 2 , KCl, H 2 O 2 , ET-1, or 4-AP (8,24) were not present in the DA of the hypoxic animals.…”

“…This indirectly suggests that Rho-kinase activity in the chicken DA was unaffected by chronic prenatal hypoxia. The chicken DA presents morphologic and functional heterogeneity along its path between the pulmonary artery and the aorta (8,24). Thus, the pulmonary side shows the structure of a muscular artery and responds to O 2 with contraction, whereas the aortic part shows the morphology of an elastic artery and relaxes in response to O 2 (8,24).…”

Developmental changes in the effects of prostaglandin E2 in the chicken ductus arteriosus

“…Thus, the pulmonary side shows the structure of a muscular artery and responds to O 2 with contraction, whereas the aortic part shows the morphology of an elastic artery and relaxes in response to O 2 (Agren et al 2007;Belanger et al 2008;BergwerV et al 1999BergwerV et al , 1996. In addition, acetylcholine, SNP and the NOindependent stimulator of sGC BAY 41-2272 induced larger relaxations in the aortic side of the vessel (Agren et al 2008).…”

“…The chicken DA presents morphological and functional heterogeneity along its path between the pulmonary artery and the aorta (Agren et al 2007;Belanger et al 2008;BergwerV et al 1999BergwerV et al , 1996. Thus, the pulmonary side shows the structure of a muscular artery and responds to O 2 with contraction, whereas the aortic part shows the morphology of an elastic artery and relaxes in response to O 2 (Agren et al 2007;Belanger et al 2008;BergwerV et al 1999BergwerV et al , 1996.…”

“…As occurs in the mammalian, the multiplicity of these vasoactive systems seems at odds with the relatively simple physiological role of the DA (Smith 1998). The main vasoconstrictor of the mammalian DA, the postnatal increase in oxygen tension, appears to play also a relevant role in the closure of the chicken DA (Agren et al 2007;Belanger et al 2008), whereas the main vasodilator of the mammalian DA, PGE 2 , is a weak relaxant agent of the chicken DA which even stimulates vasoconstrictive receptors. As the mammalian DA, the chicken DA undergoes a process of maturation to prepare the task of postnatal closure.…”