van Lier E, Pérez-Clariget R, Forsberg M
Animal and Forage Sciences Department, Faculty of Agriculture, Universidad de la República, Avda. E. Garzón 780, 12900 Montevideo, Uruguay.
Anim Reprod Sci. 2003 Nov 20;79(1-2):81-92. doi: 10.1016/s0378-4320(03)00083-6.
The aim of this study was to compare the response of cortisol in sheep of different sex and gonadal status to adrenal cortex stimulation by an ACTH analogue in the breeding and non-breeding season. Twenty-four adult Corriedale sheep were used in the non-breeding season, and 19 in the breeding season. Three weeks prior to the first trial (non-breeding season), six rams and six ewes were gonadectomised. In each trial, blood was obtained every 15min for 9h and the animals received 0.5mg of ACTH (Tetracosactid, Synacthen Depot i.m., after 1.5h of sampling. Sampling began at 10:00a.m. in the non-breeding season and at 9:00a.m. in the breeding season. Three main effects (sex, gonadal status and season) were evaluated, each with two levels (male and female, intact and gonadectomised, breeding and non-breeding season, respectively). In both seasons, the females showed higher cortisol levels after ACTH than males (P<0.001), though the difference seemed less marked in the non-breeding season. The cortisol response in the ewes was not affected by season. The rams, however, showed a lower response in the breeding season (P<0.03). Gonadectomy reduced the response in the ewes (P<0.001) but had no effect in the rams. Nevertheless, gonadectomy also eliminated the differences between the ewes and the rams, such that the intact rams had lower levels of cortisol compared to the intact females, with those of the gonadectomised animals of both sexes being intermediate between the gonad-intact groups. The results of this study confirm sex differences in ACTH induced cortisol secretion in intact sheep in vivo. Furthermore, by applying exogenous ACTH we have directly stimulated the adrenal cortex, indicating the existence of sex differences also at this level. The circulating gonadal steroids, which are responsible at least in part for the sex differences in the responses to stress, may influence cortisol secretion from the adrenal gland by direct action at the cortex.
本研究的目的是比较不同性别和性腺状态的绵羊在繁殖季节和非繁殖季节对促肾上腺皮质激素（ACTH）类似物刺激肾上腺皮质的反应。在非繁殖季节使用了24只成年考力代绵羊，繁殖季节使用了19只。在第一次试验（非繁殖季节）前三周，对6只公羊和6只母羊进行了性腺切除。在每次试验中，每15分钟采集一次血样，持续9小时，动物在采样1.5小时后接受0.5毫克ACTH（二十四肽促皮质素，长效合成促皮质素，肌肉注射）。非繁殖季节上午10:00开始采样，繁殖季节上午9:00开始采样。评估了三个主要因素（性别、性腺状态和季节），每个因素有两个水平（分别为雄性和雌性、完整和性腺切除、繁殖季节和非繁殖季节）。在两个季节中，ACTH刺激后雌性的皮质醇水平均高于雄性（P<0.001），尽管在非繁殖季节差异似乎不太明显。母羊的皮质醇反应不受季节影响。然而，公羊在繁殖季节的反应较低（P<0.03）。性腺切除降低了母羊的反应（P<0.001），但对公羊没有影响。尽管如此，性腺切除也消除了母羊和公羊之间的差异，使得完整的公羊与完整的母羊相比皮质醇水平较低，两性性腺切除动物的皮质醇水平介于性腺完整组之间。本研究结果证实了体内完整绵羊中ACTH诱导的皮质醇分泌存在性别差异。此外，通过应用外源性ACTH，我们直接刺激了肾上腺皮质，表明在这个水平上也存在性别差异。循环中的性腺类固醇至少部分负责对应激反应的性别差异，可能通过直接作用于皮质来影响肾上腺皮质醇的分泌。
