OBJECTIVETo study pharmacodynamic characteristics by oral administration aristolochic acid I (AA-I) in rats.

METHODAfter one-time oral administration of Aristolochiae manshuriensis decoction 10 g x kg(-1) and 125I labeled AA-I (containing AA-I 37.2 microg x mL(-1)), whole blood concentration of 125I-AA-I and the binding rate of serum albumin were detected in 69 normal wistar male rats. Metabolic dynamic parameters were calculated by program 3P87 with a two compartment model. The distribution ratio and ID% of nine viscera or tissue were measured and compared with other until the 40th day.

RESULTAfter oral administration, AA-I was rapidly absorbed into the blood and reached its peak at 30 minutes and lasted till 90 minutes. AA-I concentration in the blood gradually declined afterwards. 24 hours later, only few AA-I could be detected. By the 10th day, 68.5% of AA-I presented as the binding type with serum albumin. Pharmacodynamic parameters were calculated as follows: Tmax 0.74 h, Cmax 0.92 microg x mL(-1), t1/2alpha 0.68 h, t1/2beta 20.46 h, V/F 87.39 mL, CL(s) 5.85 mL x h(-1) (0.10 mL x min(-1)). On the other hand, after oral administration AA-I was rapidly distributed to all the viscera or tissue, whose peak appeared in 5 minutes and the vallecula was from 24 to 48 hours. The distribution ratio of AA-I rose in the kidney after 24 hours, and it showed the highest level in the kidney and in the liver by the 4th day compared with other organs or tissue (P < 0.05). However, the distribution ratio of AA-I in the kidney became the most dominant one after the 30th and the 40th day compared with the others (P < 0.05).

CONCLUSIONAA-I is rapidly absorbed after oral administration in rats. Its distribution has the organ specificity, which is characterized as the possible partial metabolism in the liver and the accumulation in the kidney because of rather slower elimination. The characteristics may be related to the long term nephrotoxicity of AA-I.