title: Absence of seasonal variation in antipyrine metabolism.
abstract: The induced activity of aryl hydrocarbon hydroxylase (AHH), measured by the metabolism of benzo[a]pyrene to fluorescent products in cultured human lymphocytes, shows a strong seasonal variation. The in vivo metabolism of antipyrine, which is also catalyzed by microsomal cytochrome P-450-dependent monooxygenases, has been reported to be correlated with AHH inducibility in human lymphocytes. To determine whether antipyrine metabolism also showed seasonal changes, we measured antipyrine half-life (t 1/2) in 10 nonsmokers and eight smokers at the two times of the year that correspond to the high and low peaks of inducible AHH activity as measured in lymphocytes. The mean antipyrine t 1/2 determined in all 18 subjects in summer was almost identical to that found in winter (mean +/- SEM = 10.90 +/- 0.65 and 10.96 +/- 0.78 hr). AHH activity in cultured human lymphocytes from the nonsmoking subjects was determined in control and 3-methylcholanthrene-induced cells to obtained inducibility ratios of 4.2 +/- 0.56 (SEM) in the summer and 1.4 +/- 0.14 (SEM) in winter. These results indicate that the seasonal variation in AHH inducibility in human lymphocytes is not reflected by a corresponding seasonal variation in antipyrine metabolism in vivo.
mesh_terms: D000328:Adult; D000983:Antipyrine / Q000378:metabolism*; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D004790:Enzyme Induction; D006207:Half-Life; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D012463:Saliva / Q000032:analysis; D012621:Seasons; D012907:Smoking
chemical_list: D001189:Aryl Hydrocarbon Hydroxylases; D000983:Antipyrine