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Apolipoprotein B mRNA Editing Is Preserved in the Intestine and Liver of Zinc-Deficient Rats^1,2,

Fatiha Nassir^*,,, Raymond K. Blanchard, Andrzej Mazur^*, Robert J. Cousins and Nicholas O. Davidson^,3

^* Laboratoire des Maladies Metaboliques, INRA, Theix, France Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611 Department of Medicine, University of Chicago, Chicago, IL 60637

Apolipoprotein B (apo B) mRNA editing is a site-specific, post-transcriptional cytidine deamination reaction that generates apo B48 in the mammalian small intestine and in the liver of certain animals. This reaction is mediated by an enzyme complex that includes the catalytic subunit apobec-1, a zinc-dependent cytidine deaminase. To determine the importance of zinc status to apo B mRNA editing in vivo, we examined the effects of experimentally induced zinc deficiency in rats upon hepatic and serum lipid levels and several indices of apo B gene expression. Rats were either given unlimited access to or were pair-fed a semipurified zinc-supplemented (30 mg Zn/kg) diet or were fed a zinc-deficient diet (1 mg Zn/kg) for 17 d. Significant differences were detected in the ratio of serum apo B100/B48 in the unlimited access, zinc-supplemented group compared with either zinc-deficient rats or pair-fed controls. There were no alterations in hepatic triglyceride and cholesterol concentrations, hepatic apo B mRNA abundance or apo B mRNA editing in either the small intestine or liver. Taken together, these data suggest that the altered ratios of serum apo B isomorphs seen in zinc deficiency are not mediated through changes in hepatic or intestinal apo B mRNA editing.

KEY WORDS: • rats • apolipoprotein B • gene expression • zinc deficiency

¹ Supported in part by an ARCOL grant to F.N., NIH grants DK 31127 and Institutional NRSA 07667 to R.J.C., and NIH grants HL 38180 and DK 42086 to N.O.D.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 6 November 1995. Revision accepted 3 January 1996.