Glucuronide Synthesis in the Rat and Guinea Pig Lung

Rat and guinea pig lungs were shown to possess uridinediphosphate glucuronyltransferase activity which occurs in the microsomal fraction of lung homogenates. The O-glucuronides formed were identified by using radioactive isotopes and chromatographic techniques, and by hydrolysis by β-glucuronidase.2. UDP-glucuronyltransferase activity in the lung was 1/3–2/3 of that in the liver when calc. per mg microsomal protein, but less than 10% per unit wet weight. The activity of guinea pig lung was twice that of rat lung.3. Digitonin enhanced the activity of the UDP-glucuronyltransferase of the lung 2–3-fold, compared with 4–5-fold in the liver of the guinea pig and 8–9-fold in liver of the rat. Digitonin increased the apparent Km value for 4-methyl-umbelliferone 5-fold both in the pulmonary and hepatic microsomes.