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Glucuronyltransferase Activity in Transplantable Rat Hepatomas¹

Laboratory of Biochemistry, National Cancer Institute, NIH, U. S. Department of Health, Education, and Welfare, Bethesda, Maryland 20014

Activity of the microsomal enzyme p-nitrophenylglucuronyltransferase was increased in several transplantable rat hepatomas (Morris 7787, 7316A, 7794A, and Reuber H35 and H139) when the activities were compared on a tissue protein basis with those of normal and host liver. Significant activity, comparable to that in liver, was found also in Morris 3924A and 3683 hepatomas and high- and low-catalase hepatomas. Ability to conjugate p-nitrophenol was measured with freshly prepared homogenates as well as homogenates and isolated microsomal fractions which had been activated with the nonionic detergent Triton X-100. The maximal velocity measured for microsomes indicated, in several well-differentiated hepatomas, an apparent increase in the number of enzymatic sites per unit of microsomal protein as compared with liver. Glucuronyltransferase activity of rat liver was induced to the level present in the well-differentiated hepatomas 45 hr after a single dose of 3-methylcholanthrene. ß-Glucuronidase activity towards p-nitrophenyl-ß-glucuronide, measured under conditions used to assay glucuronyltransferase activity, was low for both liver and hepatoma preparations and would not have had a determining effect on the relative glucuronyltransferase activities observed for hepatomas and livers. Tissue culture cells derived from Morris 7288C hepatoma were able to conjugate p-nitrophenol added to the medium, indicating that not only is glucuronyltransferase active in intact hepatoma cells but that the supporting systems (i.e., synthesis of uridine diphosphate glucuronic acid and cell transport) are functional also.

¹ Submitted in part to the George Washington University, Washington, D. C., in partial fulfillment of the requirements for the Master of Science degree.

Received 2/ 3/69. Accepted 6/ 5/69.