Host's defense against external challenges activates an inflammatory response regulated by a set of chemical signals, including hormones. These immunomodulatory hormones, such as corticosterone, testosterone, and melatonin, trigger the systemic immune responses responsible for inflammatory assembly and resolution. This study aimed to investigate the effects of an immune challenge on endocrine and innate immune responses in the bullfrog (Lithobates catesbeianus). Adult males were intraperitoneally injected with lipopolysaccharide (LPS; 2 mg/kg) or saline, and blood samples were collected 6 and 24 h after injection for measurement of neutrophil/lymphocyte ratio, blood leukocyte phagocytosis, plasma bacterial killing ability, and plasma levels of corticosterone, melatonin, and testosterone. Our results showed LPS-induced increased neutrophil/lymphocyte ratio and leukocyte phagocytosis, and decreased melatonin and testosterone plasma levels, which were more pronounced 24 h after injection. Overall, we conclude that LPS intraperitoneal injection can activate the innate immune response and modulate the hormonal profile of the bullfrogs, with effects more pronounced 24 h than 6 h after treatment.

宿主对外部挑战的防御激活了由一组化学信号（包括激素）调节的炎症反应。这些免疫调节激素，如皮质酮、睾酮和褪黑激素，会触发全身免疫反应，负责炎症的组装和消退。本研究旨在研究免疫攻击对牛蛙（Lithobates catesbeianus）内分泌和先天免疫反应的影响。）。成年男性腹腔注射脂多糖（LPS；2 mg/kg）或生理盐水，注射后6、24 h采集血样，测定中性粒细胞/淋巴细胞比值、血白细胞吞噬能力、血浆杀细菌能力和血浆中白细胞水平。皮质酮、褪黑激素和睾酮。我们的结果显示 LPS 诱导的中性粒细胞/淋巴细胞比率增加和白细胞吞噬作用增加，褪黑激素和睾酮血浆水平降低，注射后 24 小时更为明显。总的来说，我们得出的结论是，LPS 腹腔注射可以激活先天免疫反应并调节牛蛙的激素谱，治疗后 24 小时比治疗 6 小时效果更明显。