Stanisiewski E P, Chapin L T, Rzepkowski R A, Tucker H A
Life Sci. 1987 Aug 24;41(8):1029-35. doi: 10.1016/0024-3205(87)90692-8.
Effects of 16 (16 light:8 dark) and 8 (8L:16D) h of daily light were compared with continuous light (24L:0D) exposure on prolactin (PRL) concentrations in serum of prepubertal bulls. Concentrations of PRL in serum were 2 to 3 fold greater in bulls exposed to 24L:0D or 16L:8D as compared with 8L:16D. However, PRL concentrations attained a maximum approximately 3 weeks later in calves exposed to 24L:0D than in calves given 16L:8D. Continuous low intensity (11 to 16 lux) lighting supplemented with 16 or 8 h of high intensity (449 to 618 lux) light per day increased PRL concentrations in serum of prepubertal bulls 1.5 to 2.5 fold relative to 8L:16D (470 lux). We found that relative to 8L:16D, 1) photoperiods of 16 or 24 h of light per day increased serum concentrations of PRL in prepubertal bulls; however, the time required to achieve maximum PRL concentrations was longer in animals exposed to 24L:0D, 2) continuous low intensity lighting supplemented with 16 or 8 h of high intensity daily light also increased concentrations of PRL in serum.
将青春期前公牛血清中催乳素（PRL）浓度，对每日光照16小时（16小时光照：8小时黑暗）和8小时（8小时光照：16小时黑暗）与持续光照（24小时光照：0小时黑暗）的效果进行了比较。与8小时光照：16小时黑暗组相比，暴露于24小时光照：0小时黑暗或16小时光照：8小时黑暗组的公牛血清中PRL浓度高2至3倍。然而，暴露于24小时光照：0小时黑暗的犊牛中PRL浓度达到最大值的时间比给予16小时光照：8小时黑暗的犊牛大约晚3周。每天补充16或8小时高强度（449至618勒克斯）光照的持续低强度（11至16勒克斯）光照，使青春期前公牛血清中PRL浓度相对于8小时光照：16小时黑暗组（470勒克斯）增加了1.5至2.5倍。我们发现，相对于8小时光照：16小时黑暗组，1）每天16或24小时光照的光周期增加了青春期前公牛血清中PRL浓度；然而，暴露于24小时光照：0小时黑暗的动物达到PRL浓度最大值所需的时间更长，2）持续低强度光照并补充16或8小时每日高强度光照也增加了血清中PRL的浓度。
