Metabolism of Long-Chain Polyunsaturated Fatty Acids in Rat Kidney Cells

The metabolism of long-chain polyunsaturated fatty acids is characterized in tissues, such as liver and heart, especially from studies based on isolated cells incubated with radiolabelled fatty acid substrates. Differently, only little is known about the metabolism of fatty acids in the kidney. It is controversial whether the kidney possesses the ability to desaturate long-chain fatty acids or whether kidney cells are dependent on performed polyunsaturated fatty acids transported from the liver. In this study we used isolated rat kidney cells obtained by a perfusion technique. The cells were incubated with [1-¹⁴C]-labelled 18:3(n-3) or 20:3(n-6) fatty acids which were incorporated into complex lipids or desaturated/elongated. The lipids were separated by thin-layer chromatography and highperformance liquid chromatography. The present study shows that isolated kidney cells take up and esterify labelled long-chain polyunsaturated fatty acids in a timeand concentration-dependent manner. We have also demonstrated that isolated rat kidney cells only to a minor extent ∆6-desaturate labelled 18:3(n-3) to 18:4(n-3). Conversely, the ∆ 5-desaturation of 20:3(n-6) to 20:4(n-6) is far more active. It may thus be concluded that the kidney, at least in part, must obtain its C₂₀ and C₂₂ fatty acids from the circulation, while the active ∆5-desaturase suggests that preformed C₂₀ fatty acids can be converted to more unsaturated homologues in the kidney.