Triiodothyronine Stimulates the Expression of Sucrase–Isomaltase in Caco-2 Cells Cultured in Serum-Free Medium

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• 作者：Jumarie ; Catherine ; Herring-Gillam ; F. Elizabeth ; Beaulieu ; Jean-Franç ; ois ; Malo ; Christiane
• 刊名：Experimental Cell Research
• 出版年：1996
• 出版时间：February 1, 1996
• 年：1996
• 卷：222
• 期：2
• 页码：319-325
• 全文大小：131 K

文摘

In a previous study we have shown that triiodothyronine (T₃) added to a serum-free medium supplemented with insulin, transferrin, and selenous acid (ITS) can stimulate Caco-2 cell differentiation. In this study we have focused on the effects of T₃on sucrase activity. The results obtained demonstrate that T₃(50 nM) does not change Caco-2 cell proliferation but enhances sucrase activity from 50 to 80 % . Similar increases were observed whether or not insulin was present in the culture medium, showing that there was no synergistic effect between T₃and insulin on sucrase activity. Moreover, T₃acts specifically during the differentiation period since addition of T₃to the defined TS medium before confluency is reached does not stimulate sucrase activity. Sucrase kinetic parameters were evaluated for the first time in Caco-2 cells under various culture conditions. The presence of a single enzyme was verified, with aK_mof about 7 mMand aV_maxaround 20 nmol of substrate hydrolyzed min⁻¹mg⁻¹of protein. Our results showed that T₃did not change the enzyme's affinity for sucrose but doubled theV_max. Moreover, immunoblotting using anti-sucrase–isomaltase (SI) antibodies revealed an approximately twofold increase in the relative amount of SI immunoreactive protein in T₃-stimulated cells compared to untreated cells. Results obtained by both Northern hybridization and RT-PCR amplification showed a significant increase in SI mRNA contents. These results suggest that T₃acts primarily on sucrase expression at the mRNA level.