Sterol synthesis in the liver intestine, and lung of the guinea pig

The relative rates of sterol synthesis in the liver, ileum, and lung of the guinea pig have been studied by measuring the incorporation by tissue slices of¹⁴C-labeled acetate into digitonin-precipitable sterols. The liver showed maximum incorporation of acetate at pH 6.5, the ileum at pH 7.5, and the lung at pH 6.0. The incorporation of acetate approached the maximum rate at a concentration of 10 mM with the liver and lung and 5 mM with the ileum. Using these conditions of assay, sterol synthesis was measured in the liver, ileum, and lung of four groups of guinea pigs killed at 6-hourly intervals. Depending on the time of day, the rate of sterol synthesis in the ileum was from 6 to 14 times that in the liver, while in the lung the rate was up to 3 times that shown by the liver. Additional studies showed that all regions of the small intestine synthesized sterol at a higher rate than the liver, with the highest rate of synthesis occurring in the ileum. The rates observed in the adrenal, testis, muscle, adipose tissue, and skin indicated that these tissues are not quantitatively important sites of sterol synthesis in the guinea pig.