Stokkan K A, Vaughan M K, Reiter R J, Folkow L P, Mårtensson P E, Sager G, Lydersen C, Blix A S
Department of Arctic Biology, University of Tromsø, Norway.
Gen Comp Endocrinol. 1995 Jun;98(3):321-31. doi: 10.1006/gcen.1995.1074.
Daily variations of pineal and plasma melatonin and plasma thyroid hormones were measured in harp seals (Phoca groenlandica), grey seals (Halichoerus grypus), and hooded seals (Cystophora cristata), ranging in age from newborn to 14 days. In newborn harp seals the mean mass of the pineal gland was 273 mg (+/- 45 SEM, n = 11), containing 49 ng (median) melatonin. In newborn, 4- and 10-day-old grey seals, the pineal mass was similar, weighing on average 337 mg (+/- 74, n = 6) and containing 90 ng melatonin. Two newborn hooded seal pups had pineals weighing 520 and 1289 mg, with 254 and 7600 ng melatonin, respectively. There were no day-night differences in the pineal contents of melatonin or in the number of pineal beta-adrenergic receptors measured in newborn harp seals, and, in newborn, 4- and 10-day-old grey seals, there were no day-night or age differences in pineal melatonin content. Plasma melatonin levels were 10 times higher in newborn seals than in two 10-day-old grey seals and one 14-day-old harp seal pup. In all seal pups, the levels exhibited a 24-hr rhythmicity, with increasing night- and decreasing daytime concentrations. Plasma levels of thyroxine (T4) and triiodothyronine (T3) were generally higher in newborn seals than in 10- and 14-day-old seals or in adult females. There was no apparent 24-hr rhythmicity, but the thyroid hormone levels generally declined throughout each sampling sequence. High pineal and thyroid activities may play a thermoregulatory role in newborn seals, but the results do not indicate a stimulatory action of melatonin in the peripheral conversion of T4 to T3. It is speculated that the large and active pineal gland, particularly in newborn seals, may be related to aspects of their diving habit.
对年龄从新生到14天的格陵兰海豹（Phoca groenlandica）、灰海豹（Halichoerus grypus）和冠海豹（Cystophora cristata）的松果体和血浆褪黑素以及血浆甲状腺激素的日变化进行了测量。新生格陵兰海豹的松果体平均质量为273毫克（±45标准误，n = 11），含49纳克（中位数）褪黑素。新生、4日龄和10日龄的灰海豹，松果体质量相似，平均重337毫克（±74，n = 6），含90纳克褪黑素。两只新生冠海豹幼崽的松果体重量分别为520毫克和1289毫克，褪黑素含量分别为254纳克和7600纳克。在新生格陵兰海豹中，松果体褪黑素含量或所测松果体β-肾上腺素能受体数量没有昼夜差异，在新生、4日龄和10日龄的灰海豹中，松果体褪黑素含量也没有昼夜或年龄差异。新生海豹的血浆褪黑素水平比两只10日龄灰海豹和一只14日龄格陵兰海豹幼崽高10倍。在所有海豹幼崽中，这些水平呈现24小时节律性，夜间浓度升高而白天浓度降低。新生海豹的血浆甲状腺素（T4）和三碘甲状腺原氨酸（T3）水平通常高于10日龄和14日龄海豹或成年雌性海豹。没有明显的24小时节律性，但甲状腺激素水平在每个采样序列中总体呈下降趋势。高松果体和甲状腺活性可能在新生海豹的体温调节中起作用，但结果并未表明褪黑素对T4外周转化为T3有刺激作用。据推测，大且活跃的松果体，尤其是在新生海豹中，可能与其潜水习性的某些方面有关。
