Johnson A L
J Anim Sci. 1986 Apr;62(4):1012-20. doi: 10.2527/jas1986.6241012x.
Studies were conducted to characterize circulating concentrations of prolactin, thyroxine (T4) and triiodothyronine (T3) relative to season and the estrous cycle, and to evaluate the ability of thyrotropin-releasing hormone (TRH) to induce prolactin secretion in the horse mare. The increase in serum prolactin following the iv injection of 0, 5, 50 and 500 micrograms TRH was dose-related, while all three doses of TRH induced a significant and comparable increase in serum T4. Seasonal variations in serum prolactin were directly correlated (P less than .001) with changes in photoperiod (r = .80) and temperature (r = .61). By comparison, concentrations of T3 were inversely related to temperature (r = -.49; P less than .001), while changes in T4 were less closely associated with photoperiod (r = -.29; P = .04). There were no significant fluctuations in prolactin, T3 or T4 at any stage of the estrous cycle. These results demonstrate that concentrations of prolactin in the mare are highest during the summer and lowest during the winter, but it is unknown whether this annual rhythm is controlled by photoperiod, temperature and(or) other environmental factors.
开展了多项研究，以确定催乳素、甲状腺素（T4）和三碘甲状腺原氨酸（T3）的循环浓度与季节和发情周期的关系，并评估促甲状腺激素释放激素（TRH）诱导母马催乳素分泌的能力。静脉注射0、5、50和500微克TRH后，血清催乳素的增加与剂量相关，而所有三种剂量的TRH均诱导血清T4显著且相当程度地增加。血清催乳素的季节性变化与光周期变化（r = 0.80）和温度变化（r = 0.61）直接相关（P < 0.001）。相比之下，T3浓度与温度呈负相关（r = -0.49；P < 0.001），而T4的变化与光周期的相关性较弱（r = -0.29；P = 0.04）。在发情周期的任何阶段，催乳素、T3或T4均无显著波动。这些结果表明，母马体内催乳素的浓度在夏季最高，冬季最低，但尚不清楚这种年度节律是否受光周期、温度和（或）其他环境因素的控制。
