Department of Physiology, Institute of Biosciences, Universidade de São Paulo, São Paulo, Rua do Matão - Travessa 14 - N 101, Cidade Universitária - CEP 05508-900, São Paulo, SP, Brazil.
Institute of Environmental, Chemical, and Pharmaceutical Sciences, Universidade Federal de São Paulo, Campus Diadema- CEP 09972-270, Diadema, Brazil.
J Exp Biol. 2021 Nov 15;224(22). doi: 10.1242/jeb.243153. Epub 2021 Nov 25.
Mammals show immune up-regulation and increased plasma and local (gastrointestinal tract) concentrations of some immunoregulatory hormones, such as corticosterone and melatonin, after feeding. However, little is known about the endocrine and immune modulation in the postprandial period of ectothermic animals. This study investigated the effects of feeding on endocrine and immune responses in the bullfrog (Lithobates catesbeianus). Frogs were fasted for 10 days and divided into two groups: fasted and fed with fish feed (5% of body mass). Blood and gastrointestinal tract tissues (stomach and intestine) were collected at 6, 24, 48, 96 and 168 h to measure neutrophil/lymphocyte ratio, plasma bacterial killing ability, phagocytosis of blood leukocytes, plasma corticosterone and melatonin, and stomach and intestine melatonin. Feeding increased plasma corticosterone at 24 h and decreased it at 168 h, and increased neutrophil/lymphocyte ratio at 6, 24 and 96 h. We also observed decreased bacterial killing ability 48 h after feeding. Stomach melatonin increased after 17 days of fasting. We show that feeding activates the hypothalamic-pituitary-interrenal axis and promotes transient immunosuppression, without stimulating an inflammatory response. Increased corticosterone may mobilize energy to support digestive processes and melatonin may protect the stomach during fasting. We conclude that feeding modulates secretion of immunoregulatory hormones, initially increasing plasma corticosterone levels, followed by a decrease at the end of meal digestion, and causes systemic immune cell redistribution, increasing neutrophil/lymphocyte ratio for almost the entire period of meal digestion in bullfrogs. Also, fasting modulates secretion of melatonin in the stomach.
哺乳动物在进食后会表现出免疫上调和一些免疫调节激素（如皮质酮和褪黑素）在血浆和局部（胃肠道）中的浓度增加。然而，对于变温动物在餐后的内分泌和免疫调节知之甚少。本研究调查了摄食对牛蛙（Lithobates catesbeianus）内分泌和免疫反应的影响。牛蛙禁食 10 天，分为两组：禁食组和投喂鱼饲料组（体重的 5%）。分别在 6、24、48、96 和 168 小时采集血液和胃肠道组织（胃和肠），以测量中性粒细胞/淋巴细胞比值、血浆杀菌能力、血液白细胞吞噬作用、血浆皮质酮和褪黑素以及胃和肠褪黑素。摄食可在 24 小时增加血浆皮质酮，在 168 小时降低皮质酮，并在 6、24 和 96 小时增加中性粒细胞/淋巴细胞比值。我们还观察到摄食后 48 小时杀菌能力下降。禁食 17 天后胃褪黑素增加。我们表明摄食激活了下丘脑-垂体-肾上腺轴并促进了短暂的免疫抑制，而没有引发炎症反应。增加的皮质酮可能动员能量以支持消化过程，而褪黑素可能在禁食期间保护胃。我们的结论是，摄食调节免疫调节激素的分泌，最初增加血浆皮质酮水平，然后在进食结束时降低，导致全身免疫细胞重新分布，在牛蛙进食消化的几乎整个过程中增加中性粒细胞/淋巴细胞比值。此外，禁食调节胃褪黑素的分泌。
