Gower B A, Nagy T R, Stetson M H
School of Life and Health Sciences, University of Delaware, Newark 19716.
Gen Comp Endocrinol. 1994 Mar;93(3):459-70. doi: 10.1006/gcen.1994.1050.
Collared lemmings undergo several photoperiod-mediated seasonal physiological changes. When exposed to short photoperiod, lemmings increase in size, develop a bifid claw, and molt to a white pelage. Previous data indicate that body mass, claw size, and pelage color are influenced by hormones of testicular origin, suggesting that, on a seasonal basis, changes in production of, or sensitivity to, testicular hormones may play a role in the development of the phenotype characteristic of the ambient photoperiod. The present study was designed to determine if the active testicular hormone(s) is testosterone (T) and/or estradiol (E2) and if seasonally changing physiological traits in female lemmings are also influenced by gonadal status. Fifty-day-old lemmings, reared in 22L:2D (long day), 16L:8D (intermediate day), or 8L:16D (short day), were either gonadectomized or sham operated and given either empty Silastic implants or implants containing T (4 or 10 mm; castrated males), E2 (4 mm undiluted or diluted 1:4 with cholesterol; ovariectomized females), the aromatase inhibitor ATD (androsta-1,4,6-triene-3,17-dione; 2 x 20 mm; intact animals of both sexes), or ATD plus a 10-mm T implant (castrated males). After a 6-week treatment period, changes in body mass, bifid claw width, pelage color stage, and serum prolactin (PRL) were assessed. The effects of gonadectomy and steroid treatment depended upon photoperiod. Whereas gonadectomy increased mass gained by both sexes under intermediate and short day, under long day only females showed the positive mass response to gonadectomy. Treatment with T and E2 reversed the effect of gonadectomy on body mass under intermediate day and decreased the amount of mass gained under short day. Treatment with ATD (males) and E2 (females) indicated that E2 was the hormone responsible for the tonic, inhibitory effect of the gonads on body mass in both sexes. Claw size was most sensitive to steroid manipulation in animals housed in long day, in which all treatments had a negative influence. Gonadectomy under short day resulted in the development of a whiter pelage in both sexes. The effect of gonadectomy on pelage in female lemmings, and its reversal by E2 treatment, may have been partially due to alteration of serum PRL.
环颈旅鼠会经历几种由光周期介导的季节性生理变化。当暴露于短光周期时，旅鼠体型增大，长出双叉爪，并换毛为白色皮毛。先前的数据表明，体重、爪大小和皮毛颜色受睾丸源性激素的影响，这表明在季节性基础上，睾丸激素产生或敏感性的变化可能在环境光周期特征表型的发育中起作用。本研究旨在确定活性睾丸激素是否为睾酮（T）和/或雌二醇（E2），以及雌性旅鼠季节性变化的生理特征是否也受性腺状态的影响。将50日龄的旅鼠饲养在22小时光照：2小时黑暗（长日照）、16小时光照：8小时黑暗（中间日照）或8小时光照：16小时黑暗（短日照）条件下，对其进行性腺切除或假手术，并植入空的硅橡胶管或含有T（4或10毫米；去势雄性）、E2（4毫米未稀释或与胆固醇按1:4稀释；去卵巢雌性）、芳香化酶抑制剂ATD（雄甾-1,4,6-三烯-3,17-二酮；2×20毫米；两性完整动物）或ATD加10毫米T植入物（去势雄性）。经过6周的治疗期后，评估体重、双叉爪宽度、皮毛颜色阶段和血清催乳素（PRL）的变化。性腺切除和类固醇治疗的效果取决于光周期。在中间日照和短日照条件下，性腺切除增加了两性的体重增加量，而在长日照条件下，只有雌性对性腺切除有积极的体重反应。在中间日照条件下，用T和E2治疗可逆转性腺切除对体重的影响，在短日照条件下可减少体重增加量。用ATD（雄性）和E2（雌性）治疗表明，E2是性腺对两性体重产生持续性抑制作用的激素。在长日照饲养的动物中，爪大小对类固醇操作最为敏感，所有治疗都有负面影响。在短日照条件下进行性腺切除导致两性皮毛变白。性腺切除对雌性旅鼠皮毛的影响及其通过E2治疗的逆转，可能部分归因于血清PRL的改变。
