Czerwińska Joanna, Chojnowska Katarzyna, Kamiński Tadeusz, Bogacka Iwona, Panasiewicz Grzegorz, Smolińska Nina, Kamińska Barbara
Folia Biol (Krakow). 2015;63(4):229-34. doi: 10.3409/fb63_4.229.
Glucocorticoids (GCs) and adrenocorticotropic hormone (ACTH) are major components of the classic endocrine stress response. Free-living vertebrates are characterized by circannual changes in the baseline and/or stress-induced secretion of GCs and ACTH. In mammalian species, GC and ACTH levels vary seasonally but there is no consensus to the season in which animals have elevated GC and ACTH levels. The aim of our study was to determine, for the first time, the type and amount of glucocorticoids produced in free-living beaver (Castor fiber L.)--the largest rodent in Eurasia, and to find out whether stress-induced plasma GC and ACTH levels show seasonal variations. Blood samples were obtained from animals under general anesthesia in April (pregnancy in females), July (offspring rearing) and November (preparing for the winter). The adrenals of beavers produce both cortisol and corticosterone, and plasma cortisol levels were higher than corticosterone. In the current experiment, plasma cortisol concentrations in beavers were affected by the season. The highest stress-associated cortisol levels were noted in males in July during offspring rearing. Corticosterone and ACTH concentrations in beavers remained generally constant, regardless of the season and sex. In conclusion, seasonal changes were observed only in relation to stress-induced plasma cortisol levels in the beaver.
糖皮质激素（GCs）和促肾上腺皮质激素（ACTH）是经典内分泌应激反应的主要组成部分。自由生活的脊椎动物的特点是GCs和ACTH的基础分泌和/或应激诱导分泌存在年度周期性变化。在哺乳动物物种中，GC和ACTH水平随季节变化，但对于动物GC和ACTH水平升高的季节尚无共识。我们研究的目的是首次确定自由生活的河狸（欧亚大陆最大的啮齿动物）产生的糖皮质激素的类型和数量，并查明应激诱导的血浆GC和ACTH水平是否存在季节性变化。在4月（雌性怀孕）、7月（养育后代）和11月（为冬季做准备）从全身麻醉的动物身上采集血样。河狸的肾上腺会产生皮质醇和皮质酮，血浆皮质醇水平高于皮质酮。在当前实验中，河狸的血浆皮质醇浓度受季节影响。在7月养育后代期间，雄性河狸的应激相关皮质醇水平最高。无论季节和性别如何，河狸体内的皮质酮和ACTH浓度总体保持恒定。总之，仅在河狸应激诱导的血浆皮质醇水平方面观察到了季节性变化。
