The adrenal gland of the mouse exhibits uptake mechanisms for plasma high density lipoprotein (HDL) and low density lipoprotein (LDL). To study this uptake, we lowered the endogenous plasma lipoprotein level in mice by administering 4-aminopyrazolopyrimidine and then injected the animals with tracer amounts of human 125I-HDL or 125I-LDL intravenously. Uptake of 125I-HDL and 125I-LDL in the adrenal gland was demonstrable within 2 min after injection, and the content of radioactivity reached a steady state within 30 min. The adrenal gland accumulated 20-fold more 125I radioactivity/mg of tissue than lung or kidney. Moreover, the adrenal took up 50- to 200-fold more 125I-HDL or 125I-LDL than 125I-albumin. Adrenal uptake of both lipoproteins was reduced when adrenocorticotrophic hormone secretion was suppressed by dexamethasone. Uptake of either LDL or HDL raised the level of cholesteryl esters in the adrenal gland and suppressed the activity of microsomal 3-hydroxy-3-methylglutaryl coenzyme A reductase. The uptake mechanisms were saturable in that unlabeled lipoproteins competed with the 125I-lipoproteins for uptake. In cross-competition experiments, unlabeled LDL competed more effectively than unlabeled HDL for 125I-LDL uptake; conversely, unlabeled HDL competed more effectively than unlabeled LDL for 125I-HDL uptake. These data suggest that two different lipoprotein uptake systems supply cholesterol to the adrenal gland of the mouse, one using LDL and another using HDL.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Biological Chemistry|
|State||Published - Dec 1 1979|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology