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Biomedical subjects

A M Leung

Publications and source records attributed to A M Leung.

4 recordsLinked to original sources
PubMed1983

Activation of low density lipoprotein receptor synthesis by treatment with partially delipidated low density lipoprotein.

The role of apo-low density lipoprotein in the regulation of low density lipoprotein receptor synthesis was studied. Fibroblasts preincubated in the presence of a cholesterol-free low density lipoprotein preparation showed an increase of 50% in receptor activity. In contrast, when cells were preincubated with a similar amount of normal low density lipoproteins a 2- to 3-fold decrease of receptor activity was observed. The increase of receptor activity induced by delipidated LDL was probably due to an increase of synthesis rather than an unmasking effect since treatment with puromycin essentially abrogated the activation. The ability of the partially delipidated low density lipoproteins to elicit receptor synthesis could not be accounted for by a depletion of cellular cholesterol because a similar preparation of delipidated high density lipoproteins was unable to induce receptor synthesis but was able to reduce cellular cholesterol to the same extent. Treatment with chloroquine, a lyzosome inhibitor, blocked the ability of the delipidated low density lipoprotein to activate receptor synthesis. This suggests that degraded fragments rather than the intact delipidated lipoprotein are necessary to trigger the cell to synthesize more receptors.

Cells, Cultured↗
PubMed1982

Binding of homologous versus heterologous low density lipoproteins by different tissues of the rat.

1. The ability of five different tissues of the rat to bind homologous and heterologous (human) low density lipoprotein (LDL) was compared. 2. Human LDL was as effective as rat LDL in displacing rat [125I]LDL from the plasma membrane fraction of rat skeletal muscle. 3. Membranes from rat liver appeared to have no affinity for homologous LDL, while human LDL was slightly more effective in displacing labeled rat LDL from this tissue. 4. A similar pattern of displacement was observed in membranes derived from rat heart. 5. In contrast, membranes from both the aorta and adrenal glands of the rat displayed a significantly greater affinity for binding LDL of homologous origin. 6. These results suggest that lipoprotein receptors analogous to those described for cultured human cells may exist in the rat and that individual tissues exhibit distinctly different affinities for binding LDL of both homologous and human origin.

Adrenal Glands↗