Department of Animal Science, College of Animal Science and Veterinary Medicine, Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control, Shandong Agricultural University, Tai'an City, Shandong Province, 271018, China.
Department of Animal Science, College of Animal Science and Veterinary Medicine, Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control, Shandong Agricultural University, Tai'an City, Shandong Province, 271018, China.
Poult Sci. 2022 Mar;101(3):101669. doi: 10.1016/j.psj.2021.101669. Epub 2021 Dec 23.
The mechanism that mediates L-citrulline (L-Cit) hypothermia is poorly understood, and the involvement of nitric oxide signaling has not been fully elucidated. Therefore, this study aimed to determine L-Cit's influence on body temperature and to ascertain the central and peripheral mechanisms associated with this response. Chicks responded to intracerebroventricular (ICV) injection of L-Cit with high and low body temperatures (P < 0.05) depending on the dose tested, for both the surface and rectal temperatures. Peripheral (i.p.) L-Cit injection did not affect body temperature responses. Nitric oxide (NO) concentration and NO synthase (NOS) were influenced with varying doses of L-Cit. Hypothalamic NO was increased at 4 µg L-Cit whereas, plasma iNOS was elevated at 2µg L-Cit treatment. However, i.p. L-Cit did not change the NO content, rather it induced higher (P < 0.05) plasma tNOS and iNOS activity, and further upregulated iNOS and nNOS gene expression in the hypothalamus. In addition, ICV L-Cit potentiated a pro- versus anti-inflammatory milieu with the induction of IL-8, IL-10, and TGFβ (P < 0.05), which may be related to the changes in body temperature. Following ICV L-Cit administration, it was observed that L-Cit caused dose variable changes in the ultrastructure of hypothalamic neurons. The lowest dose was associated with a higher number of dead or degenerating neurons, whereas the highest L-Cit dose had fewer neuronal numbers with larger sizes. Therefore, this study shows that central and peripheral L-Cit administration imposes changes in body temperature, nitric oxide production, and inflammatory responses, in a dose-dependent manner.
L-瓜氨酸（L-Cit）导致体温降低的机制尚未完全阐明，一氧化氮信号通路的参与也尚未完全阐明。因此，本研究旨在确定 L-Cit 对体温的影响，并确定与这种反应相关的中枢和外周机制。根据测试的剂量，鸡对脑室内（ICV）注射 L-Cit 的反应表现为体表和直肠温度的高热和低温（P < 0.05）。外周（i.p.）注射 L-Cit 不会影响体温反应。一氧化氮（NO）浓度和一氧化氮合酶（NOS）随 L-Cit 剂量的变化而变化。4µg L-Cit 增加了下丘脑的 NO，而 2µg L-Cit 处理则增加了血浆中的 iNOS。然而，i.p. L-Cit 并未改变 NO 含量，而是诱导了更高的（P < 0.05）血浆 tNOS 和 iNOS 活性，并进一步上调了下丘脑的 iNOS 和 nNOS 基因表达。此外，ICV L-Cit 增强了促炎与抗炎之间的平衡，诱导了白细胞介素-8（IL-8）、白细胞介素-10（IL-10）和转化生长因子-β（TGFβ）的表达（P < 0.05），这可能与体温变化有关。在 ICV L-Cit 给药后，观察到 L-Cit 导致下丘脑神经元的超微结构发生剂量变化。最低剂量与更多的死亡或退化神经元相关，而最高剂量的 L-Cit 则具有较少的神经元数量和更大的尺寸。因此，本研究表明，中枢和外周给予 L-Cit 会导致体温、一氧化氮生成和炎症反应发生剂量依赖性变化。
