Circadian variation in basal plasma corticosterone and adrenocorticotropin in the rat: Sexual dimorphism and changes across the estrous cycle
Circadian variation in basal plasma corticosterone and adrenocorticotropin in the rat: Sexual dimorphism and changes across the estrous cycle
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DOI：
10.1210/en.138.9.3842
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发表时间：
1997-09-01
期刊：
影响因子：
4.8
通讯作者：
Waddell, BJ
中科院分区：
文献类型：
--
作者：
Atkinson, HC;Waddell, BJ
通过测定发情周期各阶段雄性和雌性大鼠血浆皮质酮和免疫活性(I-)ACTH，研究了大鼠下丘脑-垂体-肾上腺轴的性别二型性。一种连续的血液采样技术使评估这两种激素在个体动物体内浓度的整个昼夜范围内的协变性成为可能。所有大鼠的血浆皮质酮都有明显的昼夜节律，这种节律的程度和时间由协方差分析确定，不随性别或周期阶段而变化。然而，在整个发情周期中，皮质酮的绝对水平存在显著差异，平均每日皮质酮浓度(MESOR)从发情期的最低值(129±11 ng/ml)逐渐增加到发情前期的3天后的最高值(246±14 ng/ml)。雄性大鼠的中位皮质酮值(102+/-21 ng/ml)与发情雌性大鼠无差异，但在周期的其他各阶段均低于雌性大鼠。相反，在I-ACTH的绝对水平上没有检测到性别或周期相关的差异，尽管在所有组中都有明显的与皮质酮同步的明显的昼夜节律。因此，在所有组中都观察到血浆皮质酮和I-ACTH之间的强烈和正相关关系，但这种关系的性质在整个发情周期中发生了明显的变化，以至于斜率(即每单位浓度的I-ACTH的血浆皮质酮浓度)在雄性和发情雌性中最小，在发情前期雌性中最大。综上所述，本研究表明静息血浆皮质酮水平的性二态程度取决于发情周期阶段，发情期不存在，发情前期达到最大。此外，血浆皮质酮的这种变化没有伴随着血浆i-ACTH的相应变化，这表明肾上腺皮质对营养刺激的反应性发生了与周期相关的变化。
Sexual dimorphism in the rat hypothalamic-pituitary-adrenal axis was investigated by determination of plasma corticosterone and immunoreactive (I-) ACTH in males and in females at each stage of the estrous cycle. A serial blood-sampling technique enabled assessment of covariation of the two hormones across the full circadian range of their concentrations within individual animals. Distinct diurnal rhythms in plasma corticosterone were evident in all rats, and the degree and timing of this rhythmicity, determined by cosinor analyses, did not vary with gender or cycle stage. There were, however, marked differences in absolute levels of corticosterone across the estrous cycle, with the average daily concentration (mesor) increasing progressively from a minimum at estrus (129 +/- 11 ng/ml) to a maximum 3 days later at proestrus (246 +/- 14 ng/ml). The mesor corticosterone value in male rats (102 +/- 21 ng/ml) was not different from that in estrous females, but was lower than that in females at all other stages of the cycle. In contrast, no gender-or cycle-related differences were detected in absolute levels of I-ACTH, although distinct diurnal rhythms, synchronous with those for corticosterone, were evident in all groups. Accordingly, a strong and positive within-rat relationship between plasma corticosterone and I-ACTH was observed in all groups, but there was a clear shift in the nature of this relationship across the estrous cycle, such that the slope (i.e. concentration of plasma corticosterone per unit concentration of I-ACTH) was minimal in males and estrous females and maximal in proestrous females. In conclusion, this study shows that the extent of sexual dimorphism in resting plasma corticosterone levels is dependent on estrous cycle stage, being absent at estrus and maximal at proestrus. Moreover, this variation in plasma corticosterone was not accompanied by corresponding changes in plasma I-ACTH, suggestive of cycle-related changes in responsiveness of the adrenal cortex to trophic stimulation.