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  • Title: Metabolism and biliary excretion of 2,4,5,2',4',5'-hexachlorobiphenyl in the rhesus monkey (Macaca mulatta).
    Author: Norback DH, Mack E, Reddy G, Britt J, Hsia MT.
    Journal: Res Commun Chem Pathol Pharmacol; 1981 Apr; 32(1):71-85. PubMed ID: 6794118.
    Abstract:
    The metabolism and biliary excretion of 3H-2, 4, 5, 2', 4', 5'hexachlorobiphenyl (HCB) were studied in two rhesus monkeys (Macaca mulatta), a young, mature female and a juvenile male. This compound is a major constituent of those commercial polychlorinated biphenyl (PCB) mixtures with high chlorine content, and it is also a prevalent PCB analogue in human adipose tissue. Following cannulation of the common bile duct and duodenum, allowing collection of a known fraction of bile with return of the remaining bile into the duodenum, the animals received 3H-HCB (1 gm/kg body weight) by gastric intubation. Bile was collected daily for 3 weeks. During the 3-week period, 1.3% and 4% (from the female and male, respectively) of the administered radioactivity were excreted in the bile. As has been demonstrated for other species, the monkey apparently metabolizes and excretes HCB at a rate slower than for compounds containing two adjacent unsubstituted carbons. Approximately 2% of the bile radioactivity in the adult female and 12% in the juvenile male were extracted with organic solvents. Thin layer chromatography (TLC), using a benzene:ethyl acetate (12:1) solvent system, of the organic extracts of bile separated four major regions of radioactivity designated as I, II, II, and IV with Rf values of 0.86, 0.67, 0.58, and 0.00, respectively. Region I consisted of the parent HCB, which was identified by analysis with gas chromatography-mass spectrometry (GC-MS). Region II consisted of a metabolite identified as 2,4,5,2',4',5'-hexachloro-3-hydroxybiphenyl (OH-HCB) by analysis with GC-MS of the methylated derivative of the metabolite. Region III probably contained a more polar metabolite, which has not yet been identified. Region IV contained an even more polar material, probably including conjugates of HCB metabolites. Release of OH-HCB from the water-soluble fraction of bile in the presence of beta-glucuronidase and lack of release of OH-HCB in presence of beta-glucuronidase with saccharo-1, 4-lactone (a beta-glucuronidase inhibitor) or in the presence of aryl sulfatase with saccharo-1, 4-lactone provided evidence of water-soluble, glucuronic acid conjugates of OH-HCB in the bile. The hexachlorobiphenyl was excreted in the bile as HCB, OH-HCB, and water-soluble conjugates of HCB metabolites, probably including 2,4,5,2',4',5'-hexachloro-3-hydroxybiphenyl glucuronide. The metabolism of HCB may or may not include the formation of an arene oxide.
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