The genotoxicity and cytotoxicity of aristolochic acids is well documented, and the Aristolochiaceae plant family has been widely used in China and India for medical purposes. However, the mechanisms of aristolochic acid I (AAI) in treatment and toxicity remain to be fully elucidated. According to the theory of traditional Chinese medicine (TCM), the spleen is responsible for transportation and transformation, in which a substance is transformed, absorbed and distributed in the body. In the present study, rats were randomized into a blank group without spleen deficiency and a spleen deficiency group to investigate the metabolism of AAI. The results showed that the concentration of AAI was higher in the spleen deficiency group, compared with that of the blank group. To further elucidate this process, the expression of organic anion transporting peptide (oatp)2a1 in the rats of the two groups were examined following oral administration of AAI. It was observed that the mRNA level of oatp2a1 in the small intestine of the blank+AAI 60 min group was downregulated, compared with that in the blank group. Compared with the mRNA level of oatp2a1 in the spleen deficiency group, the expression levels in the lung and liver were downregulated in the spleen deficiency+AAI 5 min group, whereas expression levels in the kidney in the spleen deficiency+AAI 60 min group were upregulated. Based on the above results, it was hypothesized that the expression of oatp2a1 may be one of the mechanisms of AAI metabolism in rats. In TCM, the spleen and certain functions of the small intestine, are important in AAI metabolism, and affect the toxicity of AAI. In addition, the lung, liver and kidney may also be involved in spleen deficiency syndrome in rats.