Lipid storage in cultured articular chondrocytes due to prostanoid precursors and a prostanoid synthesis inhibitor

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Abstract
Lapine articular chondrocytes were subcultured in the presence or absence of the prostanoid precursors, arachidonic acid or dihomo-gammalinolenic acid, and the cyclooxygenase inhibitor indomethacin. Lipid storage was studied microscopically using the Sudan black staining method. Control chondrocyte cultures showed a weakly positive staining reaction until confluence was reached, at which point the intra-cytoplasmic lipid content decreased. Both arachidonic acid and dihomo-gamma-linolenic acid at 100 μmol/l caused a marked increase in lipid storage which continued even after confluence was achieved. 1 μmol/l concentrations were indistinguishable from controls, whereas 10 μmol/l concentrations elicited a slight increase in lipid storage compared with controls. The prostaglandin cyclooxygenase inhibitor indomethacin did not affect chondrocyte lipid storage. However, administration of a prostanoid precursor in the presence of indomethacin caused a massive increase in intra-cytoplasmic storage of lipid, eventually leading to cell death. A possible explanation is that indomethacin may alter chondrocyte lipid metabolism in the presence of substrate molecules by rechanneling lipid synthesis away from the prostaglandin pathway to other lipid synthetic pathways.