ABSTRACT
Objective To explore the in vivo exposure levels of cigarette smoking ( CS) by measuring the biomar-kers nicotine and cotinine. Methods One hundred and sixty male SD rats were divided into 15 cigarette exposure groups (10, 20 and 30 nonfilter cigarettes/day, for 2, 4, 6, 8 and 12 weeks) and a control group (without CS exposure). The rats were sacrificed at different time?points. The concentration of plasma nicotine and cotinine were measured by GC?MS/MS. Results The CS?exposed rats displayed decreased locomotor activity, ataxic gait, irregular respiration, nasal noise, and salivation after smoking exposure for 3 weeks. Rats in the CS exposure groups had lower body weight, and the reduction of body weight was time and dose related (P<0. 01). The retention time of nicotine was 7. 5 to 8. 5 min. The concentra?tion of plasma nicotine in the CS exposure groups was higher than control group (155 ± 56. 65) ng/mL. The retention time of cotinine was 11. 5 to 12. 5 min, the concentrations of plasma cotinine in CS exposure groups were higher than control group (340 ± 41. 97) ng/mL, the increase of plasma cotinine in CS groups was time?related (P<0. 05), and the exposure concentration and duration had synergistic effect on the level of plasma cotinine ( P<0. 05 ) . Conclusions CS exposurecauses structural damages in male rats. The plasma concentration of cotinine can effectively reflect the in vivo exposure lev?els of cigarette smoking, and well presents a dose?response relationship.