Regulation of lung surfactant cholesterol metabolism by serum lipoproteins |
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Authors: | Michael A Hass William J Longmore |
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Affiliation: | (1) Edward A. Doisy Department of Biochemistry, St. Louis University School of Medicine, 63104 St. Louis, MO |
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Abstract: | The isolated perfused rat lung was used as an experimental model in the study of the lipoprotein regulation of surfactant
cholesterol metabolism. Addition of low density lipoproteins (LDL) to the perfusion medium at a cholesterol concentration
of 0.5 mM had no inhibitory effect on 1-14C]-acetate incorporation into cholesterol of either the surfactant or residual fractions. Increasing the concentration of
cholesterol in the medium to 2.5 mM resulted in significant inhibition of incorporation into cholesterol of both fractions.
A similar inhibition resulted when lungs were perfused with 2.5 mM cholesterol in the form of high density lipoproteins (HDL).
No inhibition of fatty acid synthesis, measured as incorporation into cholesteryl esters, was observed. The rate of uptake
by perfused lung of cholesterol from both high and low density lipoproteins was similar. Competitive binding studies with125I-labeled lipoproteins indicated the existence of lung receptors for both classes of lipoprotein. The rate of uptake of the
apoprotein moiety of low density lipoproteins was significantly greater than that of high density lipoproteins. These data
suggest that lung cholesterol metabolism may be subject to regulation by both low and high density serum lipoproteins. |
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