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Journal of Nutrition Vol. 96 No. 1 September 1968, pp. 46-52
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Changes in Cholesterol Concentrations in Rough and Smooth Endoplasmic Reticulum and Polysomal Profiles in Rats Fed Cholesterol1,2,

Andrzej Pronczuk and Louis Charles Fillios

Massachusetts Institute of Technology, Cambridge, Massachusetts, and Boston University School of Medicine and University Hospital, Boston, Massachusetts

A significant increase in the concentration of cholesterol (expressed in terms of protein) was found in both rough and smooth endoplasmic reticulum (ER) from rats fed cholesterol, with the smooth ER consistently showing the greater degree of increase. 2-14C-mevalonate was then used to study the kinetics of newly synthesized cholesterol in vivo in both these fractions. The specific activity of newly synthesized cholesterol expressed in terms of total vesicle protein was consistently higher in the rough ER than seen in the smooth ER within the experimental period (up to 160 minutes) in control rats, but rats fed cholesterol show an opposite relationship. Also, cholesterol feeding resulted in a marked but expected depression in cholesterol synthesis. Sucrose gradient separations of ribosomes and polysomes showed that cholesterol feeding results in a relative increase in the monosomes (and possibly disomes and trisomes) at the expense of the larger polysomes. Furthermore, the free ribosomal protein (per liver) is significantly increased in rats fed cholesterol and accounts in part for the previously observed depression in hepatic protein synthesis in vivo and in vitro. The possible involvement of membranes in the intracellular transport of cholesterol is discussed.

1 Supported by Public Health Service Research Grants nos. HE 11073 and HE 07327 from the National Heart Institute. Part of this work was carried out during the tenure of Louis C. Fillios as an Established Investigator of the American Heart Association and constituted part of the thesis requirement of Andrzej Pronczuk at the Massachusetts Institute of Technology, Cambridge, Massachusetts.

2 Part of these data were included in a preliminary report at the Annual Meeting of the Federation of American Societies for Experimental Biology, Chicago, Illinois, 1967.

Manuscript received 13 March 1968.




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