Bernier M, Laferrere B, Jaillard C, Clerget M, Saez J M
Endocrinology. 1986 Jun;118(6):2254-61. doi: 10.1210/endo-118-6-2254.
We have examined the role of the NaK-ATPase pump activity on the ligand-induced down-regulation of gonadotropin receptors in cultured porcine Leydig and Sertoli cells. In both cells, inhibition of the NaK pump by ouabain produced a depletion of intracellular K+ levels (ID50, 10(-7) M) after a lag period of about 8 h. In the absence of ligand, the number of FSH receptors in ouabain-treated Sertoli cells was unaffected or slightly reduced, whereas a 2-fold increase in the number of human CG (hCG)/LH receptors with small changes in the binding affinity was observed in Leydig cells treated by ouabain. The effect of ouabain was dose dependent. Differences were also observed in the down-regulation process of gonadotropin receptors in ouabain-treated cells. The hCG-induced receptor loss in Leydig cells was completely reversed by ouabain whereas the drug had no effect on ligand-induced loss of FSH receptors in Sertoli cells. Similar results were observed when the cells were incubated in K+-free medium. Kinetics studies with labeled hCG have shown that ouabain treatment slows down significantly the rate of [125I]iodo-hCG internalization (t 1/2, 18 h; control cells, t 1/2, 6 h), but had no effect on the degradation of internalized hormone. The internalization of receptor-bound [125I]iodo-hCG was also reduced when Leydig cells were incubated in K+-free medium, but was restored when this medium was supplemented with rubidium. The influence of the NaK pump on the receptor regulation of a ligand common to both types of cells, such as epidermal growth factor, was studied under the same experimental conditions. Neither ouabain nor K+-free medium were able to prevent the epidermal growth factor-induced reduction of receptor levels in Leydig and Sertoli cells. Thus, it appears that modulation of ligand-induced receptor loss by depletion of cellular K+ levels is not dependent on the cell type, but on the ligand-receptor complex. The data also show a striking difference in the dynamics of gonadotropin-receptor interaction of two structurally related hormones.
我们研究了钠钾 - ATP酶泵活性在配体诱导的培养猪睾丸间质细胞和支持细胞中促性腺激素受体下调中的作用。在这两种细胞中，哇巴因抑制钠钾泵后，经过约8小时的延迟期，细胞内钾离子水平出现耗竭（半数抑制浓度，10⁻⁷ M）。在无配体的情况下，哇巴因处理的支持细胞中促卵泡激素（FSH）受体数量未受影响或略有减少，而在哇巴因处理的睾丸间质细胞中，人绒毛膜促性腺激素（hCG）/促黄体生成素（LH）受体数量增加了2倍，结合亲和力有小的变化。哇巴因的作用呈剂量依赖性。在哇巴因处理的细胞中促性腺激素受体的下调过程也观察到差异。哇巴因完全逆转了hCG诱导的睾丸间质细胞中受体的丢失，而该药物对支持细胞中配体诱导的FSH受体丢失没有影响。当细胞在无钾培养基中孵育时观察到类似结果。用标记的hCG进行的动力学研究表明，哇巴因处理显著减慢了[¹²⁵I]碘 - hCG内化速率（半衰期，18小时；对照细胞，半衰期，6小时），但对内化激素的降解没有影响。当睾丸间质细胞在无钾培养基中孵育时，受体结合的[¹²⁵I]碘 - hCG的内化也减少，但当该培养基补充铷时恢复。在相同实验条件下研究了钠钾泵对两种细胞共有的配体（如表皮生长因子）受体调节的影响。哇巴因和无钾培养基均不能阻止表皮生长因子诱导的睾丸间质细胞和支持细胞中受体水平的降低。因此，似乎通过细胞内钾离子水平耗竭对配体诱导的受体丢失的调节不依赖于细胞类型，而是依赖于配体 - 受体复合物。数据还显示了两种结构相关激素在促性腺激素 - 受体相互作用动力学上的显著差异。
