ApoA-I secretion by rabbit intestinal mucosa cell cultures |
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Authors: | Ting L Carlson Bruce A Kottke |
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Affiliation: | (1) Atherosclerosis Research Unit, Mayo Clinic and Foundation, 55905 Rochester, Minnesota |
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Abstract: | Lipid and apolipoprotein (apo) A-I concentrations in different density fractions of New Zealand White (NZW) and Watanabe (WHHL)
rabbit plasma were studied. Aside from the low plasma apoA-I and high density lipoprotein (HDL) cholesterol levels in WHHL
rabbits, the distribution of apoA-I was also different between the two rabbits. ApoA-I was concentrated in both the HDL2 and HDL3 fractions of NZW rabbits but was found primarily in the HDL3 fraction of WHHL rabbits. ApoA-I secretion in these two rabbits was further studiedin vitro by using intestinal and hepatocyte cell cultures. ApoA-I secretion was highest from cultures of the duodenum and the proximal
end of the jejunum; whereas, cell cultures of the distal end of the small intestine secreted very little apoA-I into the medium.
Intestinal cell cultures from WHHL rabbits secreted less, but significant amounts of, apoA-I compared to that of NZW rabbits.
ApoA-I was most concentrated in the density range of 1.12–1.21 (HDL3) fraction in medium containing 10% fetal calf serum (FCS). Serum-free medium promoted apoA-I secretion by intestinal cell
cultures that was mostly found in the d>1.21 (lipoprotein-deficient) fraction. Hepatocytes isolated from the same rabbits
by collagenase perfusion secreted little apoA-I, and it was found only in the d>1.21 fraction. The addition of oleic acid
into the culture medium with 10% FCS decreased the secretion of total apoA-I and HDL by intestinal cell cultures and increased
the secretion of very low density lipoprotein (VLDL) and intermediate density lipoproteins (IDL). The results indicate that
intestinal cells, not hepatocytes, are responsible for the secretion of apoA-I and HDL3 in rabbits, and that the secretion may be regulated under different nutritional conditions. |
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