Location and regulation of ldl receptors in intestinal
epithelium.
Fong, Loren G., Sharon E. Fujishima, Michael C. Komaromy, Youngmi K.
Pak, Jeff L. Ellsworth, and Allen D. Cooper.
Research Institute, Palo Alto Medical Foundation, Palo Alto, CA
94301, Department of Medicine, Stanford University, Stanford, CA
94303
APStracts 2:0015G, 1995.
The expression, distribution and some aspects of the regulation of LDL
receptors in rat intestinal epithelial cells were examined. Cells
prepared by a perfusion technique provided a pure preparation of
epithelial cells and could be manipulated to produce crypt-villus
units or villi alone. On a total protein basis, the abundance of LDL
receptors in villus cell membranes was half that in hepatic
membranes. The level of receptors in both tissues was reduced by
feeding an atherogenic diet, but was increased only in the liver by
ethinyl estradiol-induced hypocholesterolemia. The level of LDL
receptor mRNA in intestinal epithelial cells was somewhat lower than
in liver. Regulation of LDL receptor mRNA was similar to that of
protein. As judged by the ratio of mRNA in villus cells compared to
the villus-crypt unit and nuclear run-on assay for LDL receptor gene
transcription, we conclude that LDL receptor mRNA is produced in the
villus cells. The effect of fat feeding was regulated at the level of
transcription. Expression in villus cells in ileum was several-fold
higher than in jejunum and higher than in the liver. Together the
results suggest serum cholesterol level is not the prime determinant
of LDL receptor level in intestine, but LDL degradation in this organ
may be regulated by factors in the lumen.
Received 16 September 1994; accepted in final form 23 January
1995.
APS Manuscript Number G354-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.