Everts M E, Verhoeven F A, Bezstarosti K, Moerings E P, Hennemann G, Visser T J, Lamers J M
Department of Internal Medicine III, Erasmus University Medical School, Rotterdam, The Netherlands.
Endocrinology. 1996 Oct;137(10):4235-42. doi: 10.1210/endo.137.10.8828482.
The uptake and metabolism of T3 and T4 were investigated in cardiomyocytes isolated from 2-day-old rats. Myocytes (2-5 x 10(5) cells/well) were cultured for 1 day in medium with 5% horse serum-5% FCS and subsequently for 4 days without serum; in some cases myocytes were cultured with serum throughout the culture period. Experiments were performed at 37 C in medium with 0.5% BSA for measurement of [125I]T3 (200,000 cpm; 200 pM) uptake and with 0.1% BSA for measurement of [125I]T4 (200,000 cpm; 350 pM) uptake. Uptake of [125I]T3, expressed as femtomoles per picomolar concentration of free hormone, with any incubation time between 15 min and 24 h was at least 2-fold higher than that of [125I]T4. Neither T3 nor T4 was deiodinated within 24 h. This was observed in cells cultured in the absence or presence of serum. After 15 min of incubation, [125I]T3 uptake was 0.048 +/- 0.002 fmol/pM free T3 (n = 9), and [125I]T4 uptake was 0.018 +/- 0.003 fmol/pM free T4 (n = 9). Although [125I]T3 uptake was reduced by 31-40% (P < 0.05) by coincubation with 100 nM to 10 microM unlabeled T3, that of [125I]T4 was not affected by 1 nM to 10 microM unlabeled T4, nor was [125I]T3 uptake reduced by 10 microM unlabeled T4. Preincubation (30 min) and incubation (15 min) with 10 microM oligomycin reduced cellular ATP by 56% (P < 0.05) and [125I]T3 uptake by 73% (P < 0.05), but had no effect on [125I]T4 uptake. Similarly, [125I]T3 uptake, but not [125I]T4 uptake, was dependent on temperature and partly dependent on the Na+ gradient, as shown by the inhibitory effect of 10 microM monensin (27%; P < 0.05). The effect of aromatic amino acids (2 mM) on [125I]T3 uptake increased in the order phenylalanine < tyrosine < tryptophan. It is concluded that T3 is taken up in neonatal cardiomyocytes by an energy-dependent carrier-mediated mechanism that is also partly dependent on the Na+ gradient. Such a transport mechanism for T4 is not present in the neonatal heart, but it may appear later during development.
对从2日龄大鼠分离的心肌细胞中T3和T4的摄取及代谢进行了研究。将心肌细胞（2 - 5×10⁵个细胞/孔）在含5%马血清 - 5%胎牛血清的培养基中培养1天，随后在无血清条件下培养4天；在某些情况下，心肌细胞在整个培养期间都在含血清的条件下培养。实验在37℃下于含0.5%牛血清白蛋白的培养基中进行，用于测量[¹²⁵I]T3（200,000 cpm；200 pM）的摄取，在含0.1%牛血清白蛋白的培养基中进行，用于测量[¹²⁵I]T4（200,000 cpm；350 pM）的摄取。以每皮摩尔游离激素浓度的飞摩尔数表示的[¹²⁵I]T3摄取，在15分钟至24小时的任何孵育时间内，至少比[¹²⁵I]T4高2倍。在24小时内，T3和T4均未发生脱碘。在无血清或有血清培养的细胞中均观察到这一现象。孵育15分钟后，[¹²⁵I]T3摄取为0.048±0.002飞摩尔/皮摩尔游离T3（n = 9），[¹²⁵I]T4摄取为0.018±0.003飞摩尔/皮摩尔游离T4（n = 9）。虽然与100 nM至10 μM未标记的T3共同孵育会使[¹²⁵I]T3摄取降低31 - 40%（P < 0.05），但1 nM至10 μM未标记的T4对[¹²⁵I]T4摄取无影响，10 μM未标记的T4也不会降低[¹²⁵I]T3摄取。用10 μM寡霉素预孵育（30分钟）和孵育（15分钟）会使细胞ATP降低56%（P < 0.05），[¹²⁵I]T3摄取降低73%（P < 0.05），但对[¹²⁵I]T4摄取无影响。同样，[¹²⁵I]T3摄取依赖于温度且部分依赖于Na⁺梯度，10 μM莫能菌素的抑制作用表明了这一点（27%；P < 0.05），而[¹²⁵I]T4摄取则不然。芳香族氨基酸（2 mM）对[¹²⁵I]T3摄取的影响按苯丙氨酸<酪氨酸<色氨酸的顺序增加。结论是，T3通过能量依赖的载体介导机制被新生心肌细胞摄取，该机制也部分依赖于Na⁺梯度。新生心脏中不存在T4的这种转运机制，但可能在发育后期出现。
