PMID: 490057Sep 1, 1979Paper

Distribution of 3-hydroxy-3-methylglutaryl coenzyme A reductase and alkaline phosphatase activities in isolated ileal epithelial cells of fed, fasted, cholestyramine-fed, and 4-aminopyrazolo[3,4-d]pyrimidine-treated rats.

Journal of Lipid Research
S R PaniniH Rudney

Abstract

3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase, E.C. 1.1.1.34), the major rate-limiting enzyme of the sterol biosynthetic pathway, was studied in ileal epithelial cells isolated in a villus-to-crypt gradient according to Weiser (Weiser, M. M. 1973. J. Biol. Chem, 248:2536-2541). Alkaline phosphatase (E.C. 3.1.3.1) served as a marker for the mature villus cells. Protease effects on activity determinations were negligible. The intracellular location of HMG-CoA reductase could not be precisely determined. The activity of ileal reductase was predominantly associated with the less differentiated lower villus and crypt cells, while the reverse gradient occurred with alkaline phosphatase. This distribution of enzymes persisted in both fed and fasted rats injected with control saline-phosphate, although fasting decreased total reductase units in the ileum by 86% in 72 hr. Treatment with cholestyramine and with 4-aminopyrazolo[3,4-d]pyrimidine (APP) enhanced reductase activity in ileal cells. The percent stimulation in both cases was higher in the upper villus cells than in the crypt cells, leading to abolition of the gradient in enzyme activity. However, APP treatment caused a 98% loss in total alkaline phosphatase ...Continue Reading

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