Lee J H, Hung C F, Ho C C, Chang S H, Lai Y S, Chung J G
Department of Surgery, China Medical College Hospital, Taichung, Taiwan, Republic of China.
Neurochem Int. 1997 Oct;31(4):533-40. doi: 10.1016/s0197-0186(97)00019-3.
N-Acetyltransferase (NAT) activity was determined in the pineal gland of frogs (Rana tigrina) of different ages using 2-aminofluorene and p-aminobenzoic acid as substrates, and assayed by high-pressure liquid chromatography. Frogs of different ages were either killed during the light phase or exposed to darkness or light for 1 min during the dark phase of the lighting cycle, then returned to their cages in darkness for 30 min before being killed. The pineal gland NAT activity of 1-month-old frogs was inhibited when the animal was nocturnally exposed to 1 min of light. Nocturnal light exposure did not inhibit NAT activity in 1-month-old frogs, even though these animal displayed clear light-dark differences in pineal gland NAT activity. Nocturnal light exposure did not inhibit night-time levels of NAT activity in 1-month-old animals which had been bilaterally enucleated, thus suggesting that this effect is retinally mediated. Pretreatment of 1-month-old and 6-month-old animals with isoproterenol (a beta-adrenoceptor agonist drug) prevented the nocturnal light-induced inhibition of NAT activity. From the different sensitivity of 1-month-old and 6-month-old animals to different intensities or durations of nocturnal light exposure it was found that the duration or intensity of light exposure was not able to inhibit nocturnal NAT activity. The NAT activity was at least 4-5-fold greater in 1-month-old frogs than in 6-month-old frogs. This is the first demonstration of the retino-pineal gland pathway that appears to produce light-induced changes in pineal glands of frogs 1-month-old or older, but this pathway only functions in 1-month-old frogs, and does not appear to function in 6-month-old frogs.
以2-氨基芴和对氨基苯甲酸为底物，采用高压液相色谱法测定不同年龄青蛙（虎纹蛙）松果体中的N-乙酰转移酶（NAT）活性。不同年龄的青蛙要么在光照阶段处死，要么在光照周期的黑暗阶段暴露于黑暗或光照1分钟，然后在黑暗中返回笼子30分钟后处死。1月龄青蛙夜间暴露于1分钟光照时，其松果体NAT活性受到抑制。夜间光照并未抑制1月龄青蛙的NAT活性，尽管这些动物的松果体NAT活性表现出明显的明暗差异。夜间光照并未抑制双侧摘除眼球的1月龄动物夜间的NAT活性水平，因此表明这种效应是由视网膜介导的。用异丙肾上腺素（一种β-肾上腺素能受体激动剂药物）预处理1月龄和6月龄动物可防止夜间光照诱导的NAT活性抑制。从1月龄和6月龄动物对不同强度或持续时间的夜间光照的不同敏感性发现，光照的持续时间或强度并不能抑制夜间NAT活性。1月龄青蛙的NAT活性至少是6月龄青蛙的4-5倍。这是首次证明视网膜-松果体途径似乎会在1月龄及以上青蛙的松果体中产生光诱导变化，但该途径仅在1月龄青蛙中起作用，在6月龄青蛙中似乎不起作用。
