Expression of lipoprotein receptor and apolipoprotein E genes by perinatal rat lipid-laden pulmonary fibroblasts.
Lipid-laden interstitial fibroblasts (LIFs) are abundant during alveolar septal formation in rats and accumulate droplets of neutral lipids. The mechanisms controlling lipid acquisition by LIFs are incompletely understood and accumulation varies during postnatal development, because lipid droplets are usually a transient phenotype. We hypothesized that plasma lipoproteins may be an important source of lipids and that the cells may alter their acquisition of lipoproteins by changing the expression of lipoprotein receptors and apolipoprotein E. We quantified the accumulation low-density lipoproteins (LDLs) and very-low-density lipoproteins (VLDLs) by LIFs and the expression of LDL and VLDL receptors mRNA and protein at various perinatal ages and found no significant age-related differences. Apolipoprotein E mRNA was maximal at postnatal day 15, whereas immunoreactive apolipoprotein E protein was maximal at gestational day 21, suggesting complex regulation. Our findings indicate that the age-related difference in the lipid droplet contents of LIFs is not primarily related to differences in LDL or VLDL receptor expression. They suggest that changes in the quantities of plasma lipoproteins, which are presented to LIFs in the lung at various perinatal ages, are more likely to be responsible for age-related alterations in lipid droplet size and abundance.
McGowan
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Department of Veterans Affairs Research Service, Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, Iowa, USA.
Doro
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Jackson
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D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001057:Apolipoproteins E / Q000235:genetics*; D002478:Cells, Cultured; D005333:Fetus / Q000502:physiology*; D005347:Fibroblasts / Q000502:physiology; D015870:Gene Expression; D008055:Lipids / Q000097:blood; D008077:Lipoproteins, LDL / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000196:embryology* / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011973:Receptors, LDL / Q000235:genetics; D018110:Receptors, Lipoprotein / Q000235:genetics*
D001057:Apolipoproteins E; D008055:Lipids; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; C036053:VLDL receptor