The use of two populations of hepatocytes with different triacylglycerol contents as a model to study the accumulation of liver lipid in the laying hen.

(1) A method has been developed to separate hepatocytes, isolated from laying hens, according to their densities, using discontinuous density-gradient centrifugation on Nycodenz. (2) The hepatocytes recovered from the interface of the 5% and 10% Nycodenz layers were rich in triacylglycerol and were termed 'fatty' hepatocytes: 'non-fatty' hepatocytes were obtained from the interface of the 15% and 30% Nycodenz layers and contained less than one-quarter as much triacylglycerol. (3) 'Fatty' hepatocytes incorporated radiolabelled glucose and glycerol into total lipid at more than twice the rate of 'non-fatty' cells: the corresponding increases in the incorporation of radiolabelled choline and valine into phospholipid and protein respectively were smaller and not statistically significant. (4) A higher proportion of glycerol and glucose incorporated into total lipid was found to be phospholipid in the 'non-fatty' hepatocytes. (5) A higher proportion of radiolabelled lipid or protein formed from glycerol or valine respectively was secreted into the medium by the 'non-fatty' hepatocytes. (6) The use of these hepatocytes as a model to study fatty liver syndromes is discussed.