Li C, Littlejohn R P, Corson I D, Suttie J M
AgResearch Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand.
Gen Comp Endocrinol. 2003 Mar;131(1):21-31. doi: 10.1016/s0016-6480(02)00625-1.
Pedicles and antlers are male deer secondary sexual characters. As such, development of these structures is under the control of androgen hormones. Pedicle growth is caused by increasing and elevated plasma testosterone (T) levels, whereas first antler transformation from a fully formed pedicle occurs when the T levels are decreasing. Castration prior to pedicle initiation abrogates future pedicle and antler formation. Female deer also have the potential to develop pedicles and antlers, but they do not normally express this phenotype due to lack of sufficient androgen stimulation. Previous studies have shown that female white-tailed deer could be readily induced to grow pedicles as well as antlers by singular administration of exogenous androgens (EA), but in red deer (Cervus elaphus) singular or irregular EA treatment could only stimulate castrated male, normal or ovariectomised females to grow pedicles, but not antlers. The present study was set out to test whether these EA-induced pedicles in red deer failed to give rise to antlers was because they were constitutively incapable of doing so, or because the plasma T profile naturally exhibited in intact stags was not achieved by the androgen treatment used in these previous studies. Eight castrated red deer stag calves, 3 freemartins (females which were born co-twin to males), and 3 normal female red deer were used in the present study and treated with EA, either as biweekly injections for the castrates or as implants for freemartin and females until the late stage of pedicle growth. Blood sampling was carried out biweekly for the analyses of plasma T and IGF1 concentration. The results showed that the natural plasma T profile in the experimental deer was successfully mimicked through regular EA treatment and subsequent withdrawal at late pedicle growth stage. All castrated males, 2 out of 3 freemartin, and 1 out of 3 normal female red deer formed not only pedicles, but also antlers. Based on these results, we conclude that EA-induced pedicles at least in red deer of the genus Cervus, like those in the genus Odocoileus, are constitutively capable of giving rise to antlers, if they are of sufficient height.
角柄和鹿角是雄性鹿的第二性征。因此，这些结构的发育受雄激素的控制。角柄生长是由血浆睾酮（T）水平升高引起的，而当T水平下降时，完全形成的角柄会首次转变为鹿角。在角柄开始生长之前进行阉割会消除未来角柄和鹿角的形成。雌性鹿也有发育角柄和鹿角的潜力，但由于缺乏足够的雄激素刺激，它们通常不会表现出这种表型。先前的研究表明，通过单次注射外源性雄激素（EA），雌性白尾鹿很容易被诱导生长角柄和鹿角，但在马鹿（Cervus elaphus）中，单次或不规律的EA处理只能刺激阉割后的雄性、正常或去卵巢的雌性生长角柄，而不能刺激它们生长鹿角。本研究旨在测试这些EA诱导的马鹿角柄未能长出鹿角是因为它们本质上就无法做到，还是因为这些先前研究中使用的雄激素处理未能达到完整雄鹿自然表现出的血浆T水平。本研究使用了8只阉割后的马鹿幼鹿、3只异性孪生母犊（与雄性孪生出生的雌性）和3只正常雌性马鹿，对它们进行EA处理，阉割后的幼鹿每两周注射一次，异性孪生母犊和雌性则植入EA，直到角柄生长后期。每两周进行一次采血，以分析血浆T和IGF1浓度。结果表明，通过定期EA处理并在角柄生长后期停药，成功模拟了实验鹿的自然血浆T水平。所有阉割后的雄性、3只异性孪生母犊中的2只以及3只正常雌性马鹿中的1只不仅形成了角柄，还形成了鹿角。基于这些结果，我们得出结论，至少在鹿属的马鹿中，EA诱导的角柄，就像白尾鹿属中的角柄一样，如果它们足够高，本质上就能够长出鹿角。
