Day M L, Imakawa K, Pennel P L, Zalesky D D, Clutter A C, Kittok R J, Kinder J E
Biol Reprod. 1986 Oct;35(3):549-53. doi: 10.1095/biolreprod35.3.549.
The hypotheses that secretion of luteinizing hormone (LH) varies with season and that estradiol may modulate the seasonal fluctuation in secretion of LH in cows were investigated. Seven mature cows were ovariectomized approximately 30 days before initiation of the experiment. Three of the ovariectomized cows (OVX-E2) were administered a subcutaneous estradiol implant that provided low circulating levels of 17 beta-estradiol. The remaining 4 cows (OVX) were not implanted. From December 21, 1982, to September 20, 1984, blood samples were collected sequentially (at 10-min intervals for 6 h) at each summer and winter solstice, and each spring and autumn equinox. In addition, from March 17, 1983, to March 17, 1984, sequential samples were collected midway between each solstice and equinox. Concentration of LH was measured in all samples, and concentration of estradiol was measured in pools of samples. An annual cycle in mean serum concentration of LH and amplitude of LH pulses was detected in both groups of cows. The seasonal pattern did not differ in the two treatment groups. Serum concentration of LH and amplitude of LH pulses were highest around the spring equinox, decreased gradually to the autumn equinox, and then increased and peaked again during the following spring equinox. Frequency of LH pulses and concentration of estradiol in serum did not vary with season. Circulating concentrations of LH and amplitude of pulses tended to be higher in OVX-E2 than OVX cows throughout the experimental period. Frequency of pulses of LH was lower in OVX-E2 than OVX cows throughout the experiment. Concentrations of estradiol were higher in the implanted cows.(ABSTRACT TRUNCATED AT 250 WORDS)
研究了促黄体生成素（LH）分泌随季节变化以及雌二醇可能调节奶牛LH分泌季节性波动的假说。在实验开始前约30天，对7头成年母牛进行卵巢切除术。其中3头卵巢切除的母牛（OVX-E2）植入皮下雌二醇植入物，以提供低循环水平的17β-雌二醇。其余4头母牛（OVX）未植入。从1982年12月21日至1984年9月20日，在每个夏至、冬至、春分和秋分时依次采集血样（每隔10分钟采集一次，共6小时）。此外，从1983年3月17日至1984年3月17日，在每个至点和分点之间的中间时段依次采集样本。测定所有样本中的LH浓度，并测定样本池中的雌二醇浓度。在两组母牛中均检测到LH平均血清浓度和LH脉冲幅度的年度循环。两个处理组的季节性模式没有差异。LH血清浓度和LH脉冲幅度在春分前后最高，逐渐下降至秋分，然后在次年春分期间再次升高并达到峰值。LH脉冲频率和血清中雌二醇浓度不随季节变化。在整个实验期间，OVX-E2组的LH循环浓度和脉冲幅度往往高于OVX组。在整个实验过程中，OVX-E2组的LH脉冲频率低于OVX组。植入雌二醇的母牛中雌二醇浓度较高。（摘要截短为250字）
