Metabolism of estrogens in hepatomas of different growth rates.
The activity of estrogen 16alpha-hydroxylase was measured for nine Morris hepatomas of different growth rates and host livers. Activity was measured in the microsomal fraction of the cell (100,000 X g). In the spectrum of hepatomas studied, 16alpha-hydroxylase activity was significantly decreased in parallel with the increase in hepatoma growth rate. The decrease in enzymic activity ranged from 16 to 19% for the slow-growing tumors (Hepatomas 44, 28A, and 9633), 2 to 9% for the intermediate-growing tumors (Hepatomas 38B, 7795, and 5123A), and 0% for the fast-growing tumors (Hepatomas 7288C, 7777, and 42A). Estrogen 16alpha-hydroxylase activity of the liver of tumor-bearing rats differed from that of liver of healthy animals. There was a decrease in enzymic activity ranging from 66% to 90% of normal control rats. The activity level of the host liver did not correlate with tumor growth rate. Stimulation of 16alpha-hydroxylase with phenobarbital showed a 4-fold increase in activity in normal liver and only a 2- to 3-fold increase in host livers. The slow- and intermediate-growing hepatomas showed a 1.2-to 1.4-fold increase in enzyme activity, and no activity or stimulation in the fast-growing hepatomas was observed.
D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D002455:Cell Division; D004789:Enzyme Activation / Q000187:drug effects; D004967:Estrogens / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D009374:Neoplasms, Experimental / Q000378:metabolism / Q000473:pathology; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000378:metabolism
D004967:Estrogens; D013250:Steroid Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase; D010634:Phenobarbital