Bourne R A, Tucker H A
Endocrinology. 1975 Aug;97(2):473-5. doi: 10.1210/endo-97-2-473.
Two bull calves were subjected to changes in daily illumination over a 12-week interval, with ambient temperature maintained at 22 C. When photoperiod was shortened from 16 to 8 h, serum prolactin decreased from a maximum of 57 mg/ml to a minimum of 8 ng/ml. Conversely, with another 4 bulls, increasing the photoperiod from 8 to 16 h of light caused serum prolactin concentrations to increase from 25 to 100 ng/ml. The increase in serum prolactin in response to increasing photoperiod was delayed approximately 7 weeks, whereas the response to decreasing photoperiod was delayed only about 1 week. Changes in photoperiod had no effect on serum LH concentrations. We conclude that changes in photoperiod account, at least partially, for the seasonal changes in serum prolactin previously noted in cattle.
两头公牛犊在12周的时间间隔内接受每日光照变化，环境温度维持在22摄氏度。当光周期从16小时缩短至8小时时，血清催乳素从最高57毫克/毫升降至最低8纳克/毫升。相反，对于另外4头公牛，将光周期从8小时增加至16小时光照导致血清催乳素浓度从25纳克/毫升增加至100纳克/毫升。血清催乳素对光周期增加的反应延迟约7周，而对光周期减少的反应仅延迟约1周。光周期变化对血清促黄体生成素浓度没有影响。我们得出结论，光周期变化至少部分地解释了先前在牛身上观察到的血清催乳素的季节性变化。
