Jarmak A, Zawilska J B, Nowak J Z
Klin Oczna. 1996;98(6):417-22.
Chick pineal gland synthesise melatonin in circadian rhythm, with peak values in the dark phase of an imposed light-dark illumination cycle. Light is the most important environmental factor regulating the melatonin-generating system in this gland. Exposure to light causes a dramatic decline of the night-time levels of the melatoninergic parameters. Effect of white and monochromatic lights of various wavelength on the night-time pineal gland serotonin N-acetyltransferase (NAT) activity were examined in chicks.
Male chicks (white leghorn: 3-4-week old) were used. They were purchased on the day of hatching. All animals were offered ad libitum access to standard food and water, maintained under an ambient temperature of 27 +/- 2 degrees C (chick), 60 +/- 5% humidity, and exposed to 12 hr light: dark illumination cycle for a minimum of 8-10 days before experiments. The daytime light intensity at the surface of the animals' cages was about 150 luxes. Each experiment was done at least twice. At the beginning of the fourth hour of the dark phase of the light-dark illumination cycle groups of chicks (four animals/group) were exposed to either white or monochromatic light for 5, 10, 30 or 60 min, and then killed by decapitation. In another set of experiment birds were illuminated for 5 min, returned to darkness for additional 5, 15, 60 or 120 min, and then decapitated. Decapitation was done quickly under dim red light (2 lux). Pineal glands were isolated and frozen on dry ice. The exposure of an animal to light took place in 25 x 21 cm white plastic chamber. Light produced by 5 W 14 bulbs (Osram) was passed through a cotton filter or filtered with glass, narrow band interference filters, 7 nm half-peak band-width. The spectral wavelength analysis for each interference filter was performed with the aid of Diode-Spectrophotometer, and the irradiance of the light of the three used wavelengths was measured with YSI Radiometer. The estimated peak wavelengths (Imax) of the filters were: 434 nm (blue), 548 nm (green) and 614 nm (red). The NAT activity was determined in supernatants of tissue homogenates with the radioisotopic method of Steinlechner with modifications by Nowak.
Significant decrease of the night-time NAT activity of the chick pineal gland was observed after a 5-min pulse of either white or green light. In birds illuminated by blue light a marked reduction (by about 22%) in the pineal NAT activity was found after 10-min exposure, whereas in the group of animals that were exposed to red light a significant decline of the enzyme activity in pineal gland was produced by a 30-min pulse. The enzyme activity started to increase after 15 min in the dark and reached the control values by 1 hr (red light) or 2 hrs (blue and green lights). Two hrs and 5 min after the exposure to white light (5 min light and 120 min dark) pineal NAT activity was still significantly lower (by 16%) than the activity found in the dark control group.
Suppressive effect of monochromatic (but not white) light on NAT activity was completely reversible in the pineal gland of chick.
鸡松果体以昼夜节律合成褪黑素，在设定的明暗光照周期的黑暗阶段达到峰值。光是调节该腺体褪黑素生成系统的最重要环境因素。暴露于光会导致褪黑素能参数的夜间水平急剧下降。研究了不同波长的白光和单色光对雏鸡夜间松果体血清素N - 乙酰转移酶（NAT）活性的影响。
使用雄性雏鸡（白来航鸡：3 - 4周龄）。它们在孵化当天购买。所有动物可自由获取标准食物和水，饲养在环境温度为27±2℃（雏鸡）、湿度为60±5%的条件下，并在实验前至少8 - 10天暴露于12小时光照：12小时黑暗的光照周期。动物笼表面的白天光照强度约为150勒克斯。每个实验至少进行两次。在明暗光照周期的黑暗阶段的第4小时开始，将雏鸡组（每组4只动物）暴露于白光或单色光下5、10、30或60分钟，然后断头处死。在另一组实验中，鸟类光照5分钟，再返回黑暗中5、15、60或120分钟，然后断头处死。断头在昏暗的红光（2勒克斯）下快速进行。分离松果体并在干冰上冷冻。动物暴露于光的过程在25×21厘米的白色塑料箱中进行。由5W 14灯泡（欧司朗）产生的光通过棉滤器或用玻璃、窄带干涉滤光片过滤，半峰带宽7纳米。每个干涉滤光片的光谱波长分析借助二极管分光光度计进行，并用YSI辐射计测量所使用的三种波长光的辐照度。滤光片的估计峰值波长（Imax）为：434纳米（蓝色）、548纳米（绿色）和614纳米（红色）。采用经诺瓦克修改的施泰因勒chner的放射性同位素方法测定组织匀浆上清液中的NAT活性。
在白光或绿光照射5分钟后，观察到雏鸡松果体夜间NAT活性显著降低。在蓝光照射的鸟类中，暴露10分钟后松果体NAT活性显著降低（约22%），而在红光照射的动物组中，30分钟的脉冲导致松果体中酶活性显著下降。在黑暗中15分钟后酶活性开始增加，在1小时（红光）或2小时（蓝光和绿光）后达到对照值。在暴露于白光（5分钟光照和120分钟黑暗）后2小时5分钟，松果体NAT活性仍显著低于黑暗对照组（低16%）。
单色光（而非白光）对NAT活性的抑制作用在雏鸡松果体中是完全可逆的。
