Portacaval-shunted and sham-operated male rats, fed ad libitum and of similar weight, were studied 2-3 weeks after surgery. At this time serum cholesterol levels did not differ significantly between the two groups, whereas serum triacylglycerols and phospholipids were lower in the shunted group. These animals also showed an increased serum bile acid level and an increased serum estradiol to testosterone ratio. The metabolism of native chyle labeled with [3H]cholesterol and [14C]linoleic acid or of preformed chylomicron remnants with the same labeling was studied in the groups of rats. Ten minutes after intravenous injection of chylomicron remnants 10.6 +/- 0.5% (means +/- SEM, n = 8) of the injected [3H]cholesterol and 7.6 +/- 0.4% of the [14C]linoleic acid were found per 1 g liver in the portacaval-shunted rats; the corresponding figures in the sham-operated group (n = 8) were 6.4 +/- 0.4 and 4.9 +/- 0.3, respectively (p less than 0.001 for both 3H and 14C). Thus, despite a greater than 40% reduction of liver weight induced by the shunting procedure, the total liver uptake of chylomicron remnants was not significantly decreased. The uptake of chylomicron lipids per unit liver weight was normal in the atrophic livers of portacaval-shunted rats also when very large loads of chyle were administered.