a Department of Histology and Embryology, Faculty of Veterinary Medicine , University of Warmia and Mazury in Olsztyn , Olsztyn , Poland.
Chronobiol Int. 2018 Oct;35(11):1560-1575. doi: 10.1080/07420528.2018.1496926. Epub 2018 Sep 25.
The diurnal and circadian profiles of pineal indoles, except melatonin, are poorly characterized in birds. Moreover, there are no data on the effect of sudden changes in the light-dark cycle on these profiles. Therefore, we investigated the diurnal (Experiment I) and circadian variation (Experiment II) of nine pineal indoles (tryptophan, 5-hydroxytryptophan, serotonin, N-acetylserotonin, melatonin, 5-hydroxyindole acetic acid, 5-methoxytryptophol, 5-methoxyindole acetic acid, 5-methoxytryptamine) in geese, as well as the changes in the profiles of these substances in geese subjected to a reversed light-dark cycle (Experiment III). For the first 12 weeks of life, all geese were kept under a diurnal cycle of 12 h of light and 12 h of darkness (12L:12D). In Experiment I (n = 48), they were kept under these conditions for another 14 days before being sacrificed at 2-h intervals for sampling of the pineal glands. In Experiment II, the geese (n = 48) were divided into three groups (12L:12D, 24L:0D, 0L:24D) for 10 days before sampling at 6-h intervals. In Experiment III, 24 geese were exposed to a reversed light-dark cycle before sampling at 14:00 and 02:00 on the first, second and third days after light-dark cycle reversal. To determine the content of the indoles in the goose pineals, HPLC with fluorescence detection was used. We found that, with the exception of tryptophan, all the investigated indoles showed statistically significant diurnal variation. When geese were kept in constant darkness, most of the indoles continued to show this variation, but when geese were kept in constant light, the indoles did not show significant variation. When the light-dark cycle was reversed (12L:12D to 12D:12L), the profiles of NAS, melatonin, 5-MTAM and 5-MTOL reflected the new cycle within 2 days. The content of serotonin in geese in 12L:12D was higher than that observed in other birds under these conditions, which suggests that this compound may play a special role in the pineal physiology of this species. In conclusion, our results show that the daily variations in the metabolism of melatonin-synthesis-related indoles in the goose pineal gland are generated endogenously and controlled by environmental light conditions, as in other birds. However, comparison of the results obtained with the goose to those obtained with other species (chicken, duck) unambiguously shows that the profiles of pineal indoles differ markedly between species, in both the quantitative proportions of the compounds and the characteristics of the diurnal changes. These findings provide strong arguments for the need for comparative studies.
除褪黑素外，鸟类的松果腺吲哚的昼夜和昼夜节律特征描述不足。此外，关于光照-暗循环的突然变化对这些图谱的影响尚无数据。因此，我们研究了鹅的松果腺中 9 种吲哚（色氨酸、5-羟色氨酸、血清素、N-乙酰血清素、褪黑素、5-羟吲哚乙酸、5-甲氧基色醇、5-甲氧基吲哚乙酸、5-甲氧基色胺）的昼夜（实验 I）和昼夜变化（实验 II），以及这些物质在鹅经历相反光照-暗循环时的图谱变化（实验 III）。在生命的前 12 周，所有鹅都处于 12 小时光照和 12 小时黑暗的昼夜循环中（12L:12D）。在实验 I（n=48）中，在另外 14 天内保持这些条件，然后每隔 2 小时取样松果腺一次，进行牺牲。在实验 II 中，鹅（n=48）被分为三组（12L:12D、24L:0D、0L:24D），然后在 6 小时间隔取样前进行 10 天的采样。在实验 III 中，24 只鹅在光照-暗循环颠倒后的第一天、第二天和第三天的 14:00 和 02:00 进行采样。为了确定鹅松果腺中吲哚的含量，使用 HPLC 结合荧光检测法。我们发现，除色氨酸外，所有研究的吲哚均表现出统计学上显著的昼夜变化。当鹅被置于持续黑暗中时，大多数吲哚继续表现出这种变化，但当鹅被置于持续光照下时，吲哚没有表现出明显的变化。当光照-暗循环颠倒（12L:12D 变为 12D:12L）时，NAS、褪黑素、5-MTAM 和 5-MTOL 的含量在 2 天内反映了新的周期。12L:12D 中鹅的血清素含量高于在其他鸟类中观察到的含量，这表明该化合物可能在该物种的松果体生理中发挥特殊作用。总之，我们的结果表明，鹅松果腺中与褪黑素合成相关的吲哚代谢的昼夜变化是由内源性产生的，并受环境光照条件的控制，与其他鸟类相同。然而，将鹅的结果与其他物种（鸡、鸭）的结果进行比较，明确表明，在物种间，松果腺吲哚的图谱差异明显，化合物的定量比例和昼夜变化的特征都有差异。这些发现为进行比较研究提供了有力论据。
