Journal of Lipid Research, Vol 28, 642-648, Copyright © 1987 by Lipid Research, Inc.
Effects of dietary cholesterol and hypothyroidism on rat apolipoprotein mRNA metabolism
JJ Apostolopoulos, GJ Howlett and N Fidge
The effects of dietary cholesterol and hypothyroidism on the mRNA levels of
rat apolipoproteins A-I, A-IV, and E were measured in extracts of rat liver
and rat intestine by hybridization to specific cDNA. Four groups, each
comprised of six rats, were fed diets consisting of normal laboratory rat
chow and either no supplements (control); 5% lard, 1% cholesterol, and 0.3%
taurocholic acid (CF); 5% lard, 1% cholesterol, 0.3% taurocholic acid, and
0.1% propylthiouracil (CF-PTU); or 0.1% propylthiouracil (PTU) for 32 days.
At the conclusion of the diets, serum cholesterol, triiodothyronine, and
thyroxine levels were measured. The average serum cholesterol
concentrations for the four groups were 50.4 +/- 3.7, 75.6 +/- 15.3, 135.3
+/- 41.5, and 73.3 +/- 16.4 mg/dl, respectively. The presence of
propylthiouracil in the diets significantly lowered triiodothyronine and
thyroxine levels in the serum. The mRNA levels for apolipoproteins A-I and
A-IV in rat liver decreased significantly after the feeding of the CF-PTU
diet (31 +/- 4% and 32 +/- 3% of normal, respectively) and the PTU diet (34
+/- 8% and 43 +/- 12% of normal, respectively), but showed little change
after the CF diet (88 +/- 16% and 108 +/- 15% of normal, respectively). The
effects of dietary propylthiouracil on the hepatic mRNA levels for
apolipoproteins A-I and A-IV imply a role for thyroid hormones in
regulating the mRNA levels for these apolipoproteins in rat liver. ApoE
mRNA levels in the rat liver decreased slightly after the CF-PTU diet (74
+/- 12% of normal) and after the PTU diet (73 +/- 10% of normal).(ABSTRACT
TRUNCATED AT 250 WORDS)