Iglesias J, Gonzalez-Pacanowska D, Marco C, Garcia-Peregrin E
Departamento de Bioquímica y Biología Molecular, Universidad de Granada, Spain.
Biochem J. 1989 Jun 1;260(2):333-7. doi: 10.1042/bj2600333.
The present studies were undertaken to determine whether mevalonate 5-pyrophosphate decarboxylase (EC 4.1.1.33) is subject to physiological regulation in the intestinal mucosa. Activity was determined in epithelial cells isolated in a villus-to-crypt gradient from chicks fed on different diets in order to vary the sterol flux across the intestinal epithelium. When animals were fed on cholesterol, decarboxylase activity was decreased in all the cell fractions studied, although percentages of inhibition were maximum in crypts of jejunum and ileum. In contrast, decreased sterol flux as a consequence of cholestyramine feeding stimulated decarboxylase activity, especially in villi of the duodenum, where values increased 3-fold with respect to controls. On the other hand, the total cellular sterol content was significantly increased by the cholesterol diet. In duodenum and jejunum, 20-30% of the total cholesterol was in the esterified form under these conditions. However, dietary cholestyramine did not significantly affect amounts of total cellular cholesterol in any of the cell fractions. These results demonstrate that mevalonate 5-pyrophosphate decarboxylase activity changes considerably under different dietary situations and that the existence of secondary sites in the physiological regulation of sterol synthesis in the intestinal mucosa should be considered.
本研究旨在确定甲羟戊酸5 - 焦磷酸脱羧酶（EC 4.1.1.33）在肠黏膜中是否受到生理调节。为了改变跨肠上皮的甾醇通量，在从不同饮食喂养的雏鸡的绒毛到隐窝梯度中分离的上皮细胞中测定活性。当动物喂食胆固醇时，在所研究的所有细胞组分中脱羧酶活性均降低，尽管空肠和回肠隐窝中的抑制百分比最高。相反，由于喂食消胆胺导致的甾醇通量降低刺激了脱羧酶活性，特别是在十二指肠绒毛中，其值相对于对照增加了3倍。另一方面，胆固醇饮食使细胞总甾醇含量显著增加。在这些条件下，十二指肠和空肠中总胆固醇的20 - 30%为酯化形式。然而，饮食消胆胺对任何细胞组分中的细胞总胆固醇量均无显著影响。这些结果表明，甲羟戊酸5 - 焦磷酸脱羧酶活性在不同饮食情况下变化很大，并且应考虑在肠黏膜甾醇合成的生理调节中存在次要位点。
