Differential distribution of apolipoprotein E in young and aged spontaneously hypertensive and stroke-prone rats.
OBJECTIVE
To evaluate whether the differential distribution of apolipoprotein E among lipoprotein fractions and hepatic expression of the apolipoprotein E gene are causal factors in the regulation of lipid metabolism and physiological functions in young and aged spontaneously hypertensive and stroke-prone rats.


METHODS
Biochemical analyses were performed on serum and hepatic specimens from young (2-month-old) and aged (8-month-old) spontaneously hypertensive rats, stroke-prone spontaneously hypertensive rats and normotensive Wistar-Kyoto rats. Levels of apolipoprotein E among various lipoprotein fractions were determined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Liver concentrations of apolipoprotein E mRNA were analyzed by Northern blotting and relative levels of apolipoprotein E mRNA in different strains of rats were compared. Statistical analysis was performed by measuring correlations between hepatic apolipoprotein E mRNA levels and biological parameters.


RESULTS
Levels of apolipoprotein E in high-density and low-density lipoproteins were significantly lower in hypertensive rats than in age-matched normotensive Wistar- Kyoto rats. Although there was a significant increase in high-density lipoprotein apolipoprotein E contents in all aged animals, the elevation in aged hypertensive rats was much less than that in aged normotensive rats. Levels of apolipoprotein E in the very-low-density lipoprotein fraction were diminished in young stroke-prone rats but were remarkably high in aged rats. Steady-state levels of apolipoprotein E mRNA increased with age in all strains of rats, whereas aged hypertensive rats exhibited lower apolipoprotein E mRNA levels than aged normotensive rats.


CONCLUSIONS
The distribution of apolipoprotein E among various lipoprotein fractions was dramatically altered with age, and the alteration varied among different strains of rats. The differential distribution of apolipoprotein E in young and aged spontaneously hypertensive and stroke-prone rats suggests that apolipoprotein E could be a causal factor that disturbs the homeostasis of lipids and lipoproteins and perturbs physiological functions in hypertensive rats.
Chiang
A N
AN
Institute of Biochemistry, National Yang-Ming University, Taipei, Taiwan. anchia@mailsrv.ym.edu.tw
Chang
C P
CP
Chou
Y C
YC
Huang
K Y
KY
Hu
H H
HH
D000375:Aging / Q000378:metabolism*; D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism*; D015415:Biomarkers; D015152:Blotting, Northern; D002561:Cerebrovascular Disorders / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006973:Hypertension / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D014280:Triglycerides / Q000378:metabolism
D001057:Apolipoproteins E; D015415:Biomarkers; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D012333:RNA, Messenger; D014280:Triglycerides