ApoA-I secretion by rabbit intestinal mucosa cell cultures

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 studied in 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 greater than 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 greater than 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).(ABSTRACT TRUNCATED AT 250 WORDS)