Gingrich S A, Smith P J, Shapiro L E, Surks M I
Endocrinology. 1985 Jun;116(6):2306-13. doi: 10.1210/endo-116-6-2306.
We have previously reported that 5,5'-diphenylhydantoin (DPH) inhibits total cellular and specific nuclear T3 binding by cultured GC cells, a rat pituitary tumor cell line that produces GH. DPH decreased competitively the rate of T3 accumulation by GC cells and noncompetitively inhibited specific nuclear T3 binding as well. To determine the biological consequences of these DPH effects on cellular and nuclear T3 binding, we studied the effect of DPH on the growth rate and GH production of GC cells cultured in Dulbecco's Modified Eagle's Medium with 10% serum. Incubation with T3 stimulated the GC cell growth rate in a dose-dependent manner. The half-maximal growth rate was achieved at a T3 concentration of 0.18 nM, and the maximal effect was observed at 0.4 nM T3. Addition of DPH to GC cells cultured with 0.15 nM T3 resulted in a dose-dependent decrease in the GC cell growth rate. The half-maximal depression of the rate of GC cell growth occurred at 185 microM DPH, a concentration that results in an approximately 50% decrease in cellular and nuclear T3. The DPH-induced decrease in GC cell growth was abolished by the addition of increasing concentrations of T3 (maximal concentration, 1.0 nM). Similarly, DPH effected a dose-dependent decrease in GH production in cells cultured with physiological concentrations of T3 (0.15 nM). The decrease in GH production of cells incubated with 200 microM DPH was associated with a decrease of similar magnitude in GH mRNA. These findings suggested that the DPH effect on GH production was mediated at a pretranslational level. Addition of increasing concentrations of T3 up to 5 nM completely abolished the DPH-associated decrease in GH production. Finally, studies of the effects of DPH on cell growth and GH production in cultures maintained with T3-depleted conditions were carried out to detect putative agonist activity of DPH. In the present investigation, we were unable to detect agonist activity of DPH that was more than 10-15% of the effect of maximal doses of T3. The data suggest that DPH attenuates the action of T3 in GC cells, probably because of a decrease in the steady state concentrations of cellular and nuclear T3. These attributes of DPH suggest that the drug or related analogs may serve as prototypes of agents that may decrease thyroid hormone activity at target tissues.
我们之前报道过，5,5'-二苯基乙内酰脲（DPH）可抑制培养的GC细胞（一种产生生长激素的大鼠垂体肿瘤细胞系）的总细胞T3结合及特异性核T3结合。DPH竞争性降低了GC细胞积累T3的速率，并且非竞争性抑制了特异性核T3结合。为了确定DPH对细胞和核T3结合的这些作用的生物学后果，我们研究了DPH对在含10%血清的杜氏改良伊格尔培养基中培养的GC细胞生长速率和生长激素产生的影响。用T3孵育以剂量依赖性方式刺激了GC细胞的生长速率。在T3浓度为0.18 nM时达到最大生长速率的一半，在0.4 nM T3时观察到最大效应。向用0.15 nM T3培养的GC细胞中添加DPH导致GC细胞生长速率呈剂量依赖性降低。GC细胞生长速率降低一半时的DPH浓度为185 microM，该浓度导致细胞和核T3减少约50%。添加浓度不断增加的T3（最大浓度为1.0 nM）可消除DPH诱导的GC细胞生长降低。同样，DPH使在用生理浓度T3（0.15 nM）培养的细胞中生长激素的产生呈剂量依赖性降低。用200 microM DPH孵育的细胞中生长激素产生的降低与生长激素mRNA类似程度的降低相关。这些发现表明，DPH对生长激素产生的作用是在翻译前水平介导的。添加浓度不断增加直至5 nM的T3可完全消除与DPH相关的生长激素产生降低。最后，进行了DPH对在T3缺乏条件下维持的培养物中细胞生长和生长激素产生影响的研究，以检测DPH的假定激动剂活性。在本研究中，我们未能检测到DPH的激动剂活性超过最大剂量T3作用的10 - 15%。数据表明，DPH减弱了T3在GC细胞中的作用，可能是因为细胞和核T3的稳态浓度降低。DPH的这些特性表明，该药物或相关类似物可能作为可降低靶组织甲状腺激素活性的药物原型。
