Biochemical and physiological aspects of 2,5-hexanedione: endogenous or exogenous product?

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Abstract
This article reports results regarding two different physiological aspects of 2,5-hexanedione (2,5-HD). The first is the relationship between “free” 2,5-HD (the fraction of “real” 2,5-HD) and “total” 2,5-HD (2,5-HD obtained from acid hydrolysis) in urine and blood of workers exposed ton-hexane. The second part of the study is an attempt to clarify “physiological” excretion of 2,5-HD in subjects not occupationally exposed ton-hexane. The concentration of free 2,5-HD in urine of workers exposed ton-hexane is about 8% of total urinary 2,5-HD. In blood, free 2,5-HD is about 50% of the total. The serum concentration range of total and free 2,5-HD in workers from whom blood was taken was 33–418 μg/l and 14–283 μg/l respectively. In subjects not exposed ton-hexane, urinary concentration of 2,5-HD ranged between 0.17 and 0.98 mg/1, the urinary excretion rate between 0.23 and 0.57μg/min, and renal clearance between 14 and 66 ml/min. The blood concentration of 2,5-HD in nonexposed subjects was 6–30μg/1. Fluctuations typical of a circadian rhythm were not observed for 2,5-HD in blood or urine. We think that 2,5-HD is mainly a product of intermediate metabolism in the human body. Only a minimal part could derive fromn-hexane as a ubiquitous micropollutant.