Gern W A, Greenhouse S S
Department of Zoology and Physiology, University of Wyoming, Laramie 82071.
Gen Comp Endocrinol. 1988 Jul;71(1):163-74. doi: 10.1016/0016-6480(88)90307-3.
Melatonin secretion was measured from rainbow trout (Salmo gairdneri) pineal organs maintained individually under flow-through whole organ culture (superfusion) conditions. Radioimmunoassay of perfusate fractions collected during controlled photic conditions demonstrated that melatonin secretion in vitro remained basal during the photophase and underwent increases in titer during the scotophase. While amounts of melatonin (mel) secreted were characteristic of individual pineal organs, photophase values ranged between 0.25 and 0.75 ng mel/ml and scotophase values ranged from 6 to 10 ng mel/ml of perfusate. Diel melatonin secretion profiles reflected the illumination regimen, with light associated with low melatonin titer in the perfusate and darkness associated with high titer. Light pulses during a normal scotophase resulted in a depression in melatonin secretion regardless of whether it was administered early or late in the dark period. Pulses of darkness given early or late in a normal photophase resulted in increased melatonin secretion. Superfused trout pineal organs did not display endogenous rhythmicity in melatonin secretion when subjected to prolonged exposure to continuous darkness (DD), whether first exposed to entraining light/dark (LD) cycles prior to DD or exposed to DD at the initiation of superfusion. In both studies, elevated melatonin secretion gradually declined over time. But exposure to a 4:4LD cycle after DD resulted in decreased (with light) and increased (with darkness) melatonin secretion. These results demonstrate that the trout pineal organ can be maintained for extended periods of time in superfusion culture, that the trout pineal organ is very responsive to light or dark for regulating melatonin synthesis, and that an endogenous rhythm in melatonin synthesis when organs were maintained in DD was not detectable.
对在流通式全器官培养（灌注）条件下单独培养的虹鳟（Salmo gairdneri）松果体器官的褪黑素分泌进行了测定。在可控光照条件下收集的灌注液组分的放射免疫分析表明，体外褪黑素分泌在光照期保持基础水平，在暗期滴度升高。虽然分泌的褪黑素（mel）量是各个松果体器官的特征，但光照期的值在0.25至0.75 ng mel/ml之间，暗期的值在6至10 ng mel/ml的灌注液范围内。昼夜褪黑素分泌模式反映了光照方案，光照与灌注液中低褪黑素滴度相关，黑暗与高滴度相关。正常暗期的光脉冲导致褪黑素分泌减少，无论其在黑暗期的早期还是晚期给予。在正常光照期的早期或晚期给予黑暗脉冲导致褪黑素分泌增加。当长时间暴露于持续黑暗（DD）时，灌注的鳟鱼松果体器官在褪黑素分泌方面未显示出内源性节律性，无论在DD之前是否首先暴露于夹带光/暗（LD）循环，还是在灌注开始时暴露于DD。在两项研究中，升高的褪黑素分泌随时间逐渐下降。但在DD后暴露于4:4 LD循环导致褪黑素分泌减少（光照时）和增加（黑暗时）。这些结果表明，鳟鱼松果体器官可以在灌注培养中长时间维持，鳟鱼松果体器官对光或暗调节褪黑素合成非常敏感，并表明当器官维持在DD中时，褪黑素合成的内源性节律无法检测到。
