Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Warmia and Mazury in Olsztyn, Oczapowskiego 13, Olsztyn 10-719, Poland.
Int J Mol Sci. 2019 Aug 17;20(16):4022. doi: 10.3390/ijms20164022.
The regulation of melatonin secretion in the avian pineal organ is highly complex and shows prominent interspecies differences. The aim of this study was to determine the roles of direct photoreception and the internal oscillator in the regulation of melatonin secretion in the pineal organ of the domestic turkey. The pineal organs were collected from 12-, 13- and 14-week-old female turkeys reared under a 12 L:12 D cycle with the photophase from 07.00 to 19.00, and were incubated in superfusion culture for 3-6 days. The cultures were subjected to different light conditions including 12 L:12 D cycles with photophases between 07.00 and 19.00, 13.00 and 01.00 or 01.00 and 13.00, a reversed cycle 12 D:12 L, cycles with long (16 L:8 D) and short (8 L:16 D) photophases, and continuous darkness or illumination. The pineal organs were also exposed to light pulses of variable duration during incubation in darkness or to periods of darkness during the photophase. The secretion of melatonin was determined by direct radioimmunoassay. The turkey pineal organs secreted melatonin in a well-entrained diurnal rhythm with a very high amplitude. Direct photoreception as an independently acting mechanism was able to ensure quick and precise adaptation of the melatonin secretion rhythm to changes in light-dark conditions. The pineal organs secreted melatonin in circadian rhythms during incubation in continuous darkness or illumination. The endogenous oscillator of turkey pinealocytes was able to acquire and store information about the light-dark cycle and then to generate the circadian rhythm of melatonin secretion in continuous darkness according to the stored data. The obtained data suggest that the turkey pineal gland is highly autonomous in the generation and regulation of the melatonin secretion rhythm. They also demonstrate that the turkey pineal organ in superfusion culture is a valuable model for chronobiological studies, providing a highly precise clock and calendar. This system has several features which make it an attractive alternative to other avian pineal glands for circadian studies.
鸟类松果腺中褪黑素分泌的调节非常复杂，表现出明显的种间差异。本研究的目的是确定直接光感受和内部振荡器在调节家养火鸡松果腺中褪黑素分泌中的作用。从在 12L:12D 光周期下饲养的 12、13 和 14 周龄雌性火鸡中采集松果腺，光期为 07:00 至 19:00，并在灌注培养中培养 3-6 天。培养物暴露于不同的光照条件下，包括 07:00 至 19:00、13:00 至 01:00 或 01:00 至 13:00 的 12L:12D 光周期、颠倒的 12D:12L 光周期、长（16L:8D）和短（8L:16D）光期的光周期，以及连续的黑暗或光照。松果腺在黑暗中孵育时也会暴露于不同持续时间的光脉冲，或者在光期暴露于黑暗期。褪黑素的分泌通过直接放射免疫测定法确定。火鸡松果腺以高度节律性的方式分泌褪黑素，振幅非常大。直接光感受作为一种独立作用的机制，能够确保褪黑素分泌节律快速而精确地适应光暗条件的变化。松果腺在连续黑暗或光照孵育期间以昼夜节律分泌褪黑素。火鸡松果体细胞的内源性振荡器能够获取和存储关于光暗周期的信息，然后根据存储的数据在连续黑暗中产生褪黑素分泌的昼夜节律。获得的数据表明，火鸡松果腺在褪黑素分泌节律的产生和调节中具有高度自主性。它们还表明，在灌注培养中的火鸡松果腺是生物钟研究的有价值模型，提供了高度精确的时钟和日历。该系统具有几个特征，使其成为其他禽类松果腺进行昼夜节律研究的有吸引力的替代方案。
