| pubmed-article:7767866 | pubmed:abstractText | The capacity of immature intestinal epithelial crypt cells to synthesize lipids and the factors that promote their differentiation remain largely unknown. We examined the profile of lipids synthesized by a normal rat intestinal epithelial crypt cell line (IEC-6) and determined the effects of transforming growth factor beta (TGF beta), a putative crypt cell differentiating factor, on their lipid handling. Incubation of IEC-6 cells with [14C]oleic acid (20 h) resulted in lipid esterification and synthesis, mainly as triglycerides (TGs, 57 +/- 0.6%) and phospholipids (PLs, 30 +/- 0.6%), with a PL/TG ratio of 0.53. When cells were pulsed (2.5 h) with [14C]oleic acid and then maintained 20 h in medium alone, a significant elevation of the PL/TG ratio (10.2 +/- 1.3, p < 0.01) was observed, primarily accounted for by a significant decrease of the TG fraction (p < 0.01). IEC-6 cells secreted only trace amounts of lipids under the latter experimental condition. Incubation with TGF beta (20 h) significantly inhibited IEC-6 cell proliferation but did not promote the expression of cell sucrase activity. TGF beta induced a significant increase in the cellular composition of PL (p < 0.05) and a decrease in the TG fraction (p < 0.02), after a 2.5-h pulse of [14C]oleic acid. Lipid production was unaffected by TGF beta during the 20-h incubation with [14C]oleic acid. Lipid secretion into the medium remained negligible in the presence of TGF beta, after 2.5 h of incubation with substrate as above. Our findings suggest that immature crypt IEC-6 cells are capable of lipid esterification and synthesis but secrete minute amounts of lipoproteins.(ABSTRACT TRUNCATED AT 250 WORDS) | lld:pubmed |
