Effect of age on cholesterol uptake and utilization by rat adrenals: II. Lipoproteins from young and old rats.
The current study examines whether age-related changes in high density lipoproteins (HDL) influences how these particles are handled by adrenal cells. It appears that HDL from 18- to 20-month-old Sprague-Dawley rats show a seven- to eightfold increase in content of apolipoprotein E compared to HDL from 2- to 5-month-old rats. The 'aged' particles show increased binding to susceptible hepatic membranes, and show a doubling in whole particle endocytosis by cortical cells of the perfused adrenal gland and by isolated adrenal cells from all rats regardless of age. Despite this twofold increase in particle uptake, the increase in total cholesteryl ester uptake by either the perfused adrenal or incubated adrenal cells is minor, amounting to less than 10% of the total cholesteryl ester internalized. This discrepancy occurs since the high apo E content of the 'aged' HDL only affects cholesteryl ester uptake by the 'endocytic' pathway; uptake via the 'selective' pathway (where cholesteryl ester is separated from the rest of the particle at the cell surface and directly internalized) is not altered.
Reaven
E
E
Geriatrics Research, Education and Clinical Center, Department of Veterans Affairs Medical Center, Palo Alto, CA 94304, USA.
Cao
L
L
Azhar
S
S
D000302:Adrenal Cortex / Q000166:cytology / Q000378:metabolism*; D000311:Adrenal Glands / Q000166:cytology / Q000378:metabolism*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism
D008075:Lipoproteins, HDL; D011994:Recombinant Proteins; D002784:Cholesterol