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Investigations on the mechanism of the hypocholesterolemic action of 1-ethoxysilatrane

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Summary

Intraperitoneal administration of the nontoxic silicon compound, 1-ethoxysilatrane, to the rat did not cause proliferation of hepatic mitochondria or of endoplasmic reticulum, nor did it affect mitochondrial oxidative phosphorylation. The activities of cholesterol 7 α-hydroxylase in hepatic microsomes and of cholesterol oxidase in mitochondria respectively were unaffected by silatrane treatment. The rate of release of bile, whose composition remained unchanged, also was not increased in silatrane-treated animals. The results indicated that the compound did not affect the pathway of cholesterol degradation.

A progressive decrease in the activity of hepatic microsomal 3-hydroxy-3-methylglutaryl coenzyme A (HMGCoA) reductase was observed on administration of the compound over a period of three weeks. Consistent with this, cholesterol biosynthesis in liver as measured by incorporation of radioactive precursors, acetate and water but not mevalonate, was significantly decreased in silatrane-treated animals. However, enzyme-linked immunosorbant assay revealed that the concentration of HMGCoA reductase protein was not decreased by the treatment indicating that inactivated enzyme was also present in such microsomes. Addition of silatrane to microsomes in the assay system did not cause inhibition indicating that the inactivation is by an indirect mechanism. It is concluded that the hypocholesterolemic action of the compound rested entirely on the inhibition of cholesterol biosynthesis in vivo by inactivation of the rate-limiting enzyme HMGCoA reductase.

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Authors and Affiliations

  1. Department of Biochemistry, Indian Institute of Science, 560 012, Bangalore, India

    Prashant P. Mehta, T. Ramasarma & C. K. Ramakrishna Kurup

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  1. Prashant P. Mehta
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  2. T. Ramasarma
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  3. C. K. Ramakrishna Kurup
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Mehta, P.P., Ramasarma, T. & Ramakrishna Kurup, C.K. Investigations on the mechanism of the hypocholesterolemic action of 1-ethoxysilatrane. Mol Cell Biochem 97, 75–85 (1990). https://doi.org/10.1007/BF00231703

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  • DOI: https://doi.org/10.1007/BF00231703

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