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5132512 
Journal Article 
A Modified Protocol For Measuring Alterations In Human Placental Aryl Hydrocarbon Hydroxylase (AHH) Activity Associated With Environmental Chemical Exposure 
Wong, TK; Hunnicutt, C; Blanton, T; Clare KSt; Cefalo, RC; Everson, RB 
1983 
Yes 
Developments in Toxicology and Environmental Science
ISSN: 0165-2214 
11 
395-398 
English 
A modified protocol for measuring aryl-hydrocarbon-hydroxylase (AHH) activity induced by chemical exposure was examined in rat and human placenta. Pregnant female Charles-River-rats were treated with either Aroclor-1254 (11097691) at 500 milligrams per kilogram (mg/kg) body weight in corn-oil or corn-oil by gastric intubation. Animals were sacrificed 72 hours later. The maternal livers and placenta from each group of treated animals were pooled for tissue preparation. Full term human placentas were also used for comparing mixed function oxidase activity from fresh and frozen tissues. Benzo(a)pyrene (50328) (BaP) hydroxylation was determined in the AHH assay of placental homogenate by incubation for 60 minutes. The reaction mixture for the rat tissue homogenates was similar to the human placental homogenate but contained about 50 percent less BaP in the reaction mixture. The fluorescence of alkali extracted BaP phenols was measured in a spectrofluorometer. AHH activity by BaP hydroxylation in human placenta was approximately linear with respect to incubation time up to 60 minutes. Approximately 2 to 4 picomoles per milligram protein per hour (pmol/mg/protein/hour) activity was found in the rat liver supernatant. Homogenate AHH activity was similar for frozen or fresh tissue. Freezing the sample in large sections appeared to yield higher AHH activity. The efficiency of mechanical recovery of BaP decreased when increasing amounts of placental homogenate were added. No appreciable BaP metabolism was seen with placental homogenates from Aroclor-1254 treated rats or from human subjects with low to moderate AHH activity. In one human placental sample with high AHH activity, 55pmol/mg/protein/hour, a 30 percent loss of BaP was observed in the incubated sample. The authors conclude that increasing the protein concentration of placental homogenate from 2 to 6 milligrams and the length of incubation from 20 to 60 minutes allows for accumulation of more BaP products.