Nicotine and cotinine accumulation in pigmented and unpigmented rat hair

This study was performed to assess the contribution of systemic and external uptake to nicotine accumulation in hair. The systemic nicotine uptake in hair was determined in pigmented rats (Brown Norway) and albino rats (Sprague-Dawley) after subcutaneous administration of 3 doses of nicotine with osmotic minipumps [5, 10, and 20 mg/(kg x day) for 3 weeks], the highest dose also following metabolic enzyme induction. The external nicotine uptake was determined in cut hair of both strains after exposure to room-aged cigarette sidestream smoke, a surrogate for environmental tobacco smoke (nicotine concentration: 5 micrograms/liter for 1, 2, and 3 weeks). Nicotine and its metabolite cotinine were determined using capillary GC after complete alkaline digestion of the hair sample and solvent extraction. Systemic uptake: Nicotine and cotinine concentrations in hair were dose-dependent and correlated with plasma concentrations. The nicotine concentration was approximately 20 times higher in pigmented than in unpigmented hair. The cotinine concentration was approximately 10 times lower than the nicotine concentration in pigmented hair. After enzyme induction before administration, nicotine and cotinine concentrations in hair were significantly reduced in parallel to the reduced plasma concentrations, showing the influence of metabolism. External uptake: Nicotine was found in the hair of both strains, the concentration in pigmented hair being a factor of 1.5 higher than in unpigmented hair. Thus, hair pigmentation had a major influence on systemic uptake in hair and a minor influence on external uptake in hair.(ABSTRACT TRUNCATED AT 250 WORDS)