Instituto de Histologia e Embriologia, Faculdade de Medicina, Universidade de Coimbra, Polo I Rua Larga, 3004-504, Coimbra, Portugal; Centro Hospitalar e Universitário de Coimbra, Praceta Prof. Mota Pinto, 3000-075 Coimbra, Portugal.
Instituto de Histologia e Embriologia, Faculdade de Medicina, Universidade de Coimbra, Polo I Rua Larga, 3004-504, Coimbra, Portugal.
Acta Histochem. 2020 Dec;122(8):151626. doi: 10.1016/j.acthis.2020.151626. Epub 2020 Oct 15.
Mammalian lung development proceeds during the postnatal period and continues throughout life. Intricate tubular systems of airways and vessels lined by epithelial cells are developed during this process. All cells, and particularly epithelial cells, carry an array of glycans on their surfaces. N-acetylneuraminic (Neu5Ac) and N-glycolylneuraminic (Neu5Gc) acids, two most frequently-occurring sialic acid residues, are essential determinants during development and in the homeostasis of cells and organisms. However, systematic data about the presence of cell surface sialic acids in the postnatal lung and their content is still scarce. In the present study, we addressed the histochemical localization of Neu5Ac > Neu5Gc in 0-day-old rat lungs. Furthermore, both residues were separated, identified and quantified in lung membranes isolated from 0-day-old rat lungs using high-performance liquid chromatography (HPLC) methodologies. Finally, we compared these results with those previously reported by us for adult rat lungs. The Neu5Ac > Neu5Gc residues were located on the surface of ciliated and non-ciliated cells and the median values for both residues in the purified lung membranes of newborn rats were 5.365 and 1.935 μg/mg prot., respectively. Comparing these results with those reported for the adults, it was possible to observe a significant difference between the levels of Neu5Ac and Neu5Gc (p < 0.001). A more substantial change was found for the case of Neu5Ac. The preponderance of Neu5Ac and its expressive increase during the postnatal development points towards a more prominent role of this residue. Bearing in mind that sialic acids are negatively charged molecules, the high content of Neu5Ac could contribute to the formation of an anion "shield" and have a role in pulmonary development and physiology.
哺乳动物的肺发育发生在出生后时期，并持续贯穿整个生命过程。在此过程中，形成了复杂的气道和血管管状系统，这些系统由上皮细胞构成。所有细胞，特别是上皮细胞，在其表面携带一系列聚糖。N-乙酰神经氨酸（Neu5Ac）和 N-羟乙酰神经氨酸（Neu5Gc）是两种最常见的唾液酸残基，是细胞和生物体内在发育和稳态过程中的重要决定因素。然而，关于出生后肺表面唾液酸及其含量的系统数据仍然很少。在本研究中，我们研究了 0 天龄大鼠肺中 Neu5Ac > Neu5Gc 的组织化学定位。此外，我们还使用高效液相色谱（HPLC）方法，从 0 天龄大鼠肺中分离的肺膜中分离、鉴定和定量了这两种残基。最后，我们将这些结果与我们之前报告的成年大鼠肺的结果进行了比较。Neu5Ac > Neu5Gc 残基位于纤毛细胞和非纤毛细胞的表面，新生大鼠纯化肺膜中这两种残基的中位数分别为 5.365 和 1.935μg/mg prot.。将这些结果与成年大鼠的结果进行比较，可以观察到 Neu5Ac 和 Neu5Gc 水平之间存在显著差异（p < 0.001）。Neu5Ac 的变化更为显著。出生后发育过程中 Neu5Ac 的优势及其显著增加表明该残基具有更重要的作用。考虑到唾液酸是带负电荷的分子，Neu5Ac 的高含量可能有助于形成阴离子“屏蔽”，并在肺发育和生理学中发挥作用。
