Weber G M, Okimoto D K, Richman N H, Grau E G
Department of Zoology, University of Hawaii, Honolulu 96822.
Gen Comp Endocrinol. 1992 Mar;85(3):392-404. doi: 10.1016/0016-6480(92)90084-w.
This study describes simultaneous measurements of thyroid hormones, thyroxine (T4) and triiodothyronine (T3), in the oocytes and serum of a female teleost fish over a complete reproductive cycle. We have identified patterns in circulating T4 and T3 levels as well as their accumulation into oocytes during the reproductive cycle of the tilapia (Oreochromis mossambicus). This is the first description of the patterns with which thyroid hormones accumulate in teleost oocytes. The sampling strategy used in the study eliminated the possible influences of covarying environmental factors that may affect thyroid hormone levels independently of reproductive events. Hormones in serum and oocytes were measured by radioimmunoassay utilizing miniature Sephadex columns. The total content of both thyroid hormones in the oocytes increased throughout most of the ovarian cycle as the oocytes increased in size from less than 2 mg to approximately 6.5 mg by ovulation. By contrast, concentrations of thyroid hormones in the oocytes rose only during the first third of post-spawning oocyte growth (up to approximately 2 mg) before attaining plateaus at approximately 6 ng/g for T4 and 13 ng/g for T3. Serum concentrations of T4 and T3 varied in cyclical patterns during oogenesis, dropping to lows of 3.4 ng/ml (T4) and 2.7 ng/ml (T3) when the oocytes were 1.5 and 2 mg, respectively, and then increasing to 6.5 ng/ml (T4) and 4.8 ng/ml (T3) when the oocytes reach approximately 6 mg. The concentrations of both hormones decreased shortly before spawning. Maximum concentrations of thyroid hormones in the oocytes were reached approximately 10 days prior to those in the serum. Although the serum levels of T4 were greater than those of T3, the reverse was found in the oocytes. Triiodothyronine appears to be accumulated selectively over T4 and the patterns with which both thyroid hormones accumulate in the oocytes of the tilapia do not appear to be tied to serum levels.
本研究描述了在一个完整的生殖周期内，对一种雌性硬骨鱼的卵母细胞和血清中的甲状腺激素——甲状腺素（T4）和三碘甲状腺原氨酸（T3）进行的同步测量。我们已经确定了罗非鱼（莫桑比克罗非鱼）生殖周期中循环T4和T3水平的模式以及它们在卵母细胞中的积累情况。这是首次对甲状腺激素在硬骨鱼卵母细胞中积累模式的描述。该研究中使用的采样策略消除了可能独立于生殖事件而影响甲状腺激素水平的协变环境因素的潜在影响。血清和卵母细胞中的激素通过利用微型葡聚糖凝胶柱的放射免疫测定法进行测量。随着卵母细胞在卵巢周期的大部分时间里从小于2毫克长到排卵时约6.5毫克，卵母细胞中两种甲状腺激素的总含量都有所增加。相比之下，卵母细胞中的甲状腺激素浓度仅在产后卵母细胞生长的前三分之一阶段（长到约2毫克之前）上升，之后T4达到约6纳克/克、T3达到约13纳克/克的稳定水平。在卵子发生过程中，血清中T4和T3的浓度呈周期性变化，当卵母细胞分别为1.5毫克和2毫克时，降至3.4纳克/毫升（T4）和2.7纳克/毫升（T3）的低点，然后当卵母细胞达到约6毫克时，升至6.5纳克/毫升（T4）和4.8纳克/毫升（T3）。两种激素的浓度在产卵前不久下降。卵母细胞中甲状腺激素的最高浓度比血清中的最高浓度提前约10天达到。虽然血清中T4的水平高于T3，但在卵母细胞中情况相反。三碘甲状腺原氨酸似乎比T4更有选择性地积累，并且两种甲状腺激素在罗非鱼卵母细胞中的积累模式似乎与血清水平无关。
