Leong PK, Leung HY, Chan WM, Ko KM
 Division of Life Science, Hong Kong University of Science & Technology, Clear Water Bay, Hong Kong, China
“Meridian tropism” refers to the organ-specific biological action(s) produced by a Chinese herb following its oral administration, which is analogous to the concept of “bioavailability” in Western medicine. In this study, we compared the in vitro and ex vivo pharmacological actions of three herbs [namely, Dangshen (DS, Codonopsis Radix), Ranshen (RS, Ginseng Radix) and
Xiyangshen (XYS, Panacis Qinquifolii Ra-dix)] to validate their meridian tropism. We compared the in vitro and ex vivo pharmacological actions [i.e. the ability to increase splenocyte proliferation and adenosine triphosphategeneration capacity (ATP-GC)] of the ethanolic extracts of DS, RS and XYS to validate their meridian tropism. Results showed that DS, RS and XYS (at 30 - 300 μg/mL) can both stimulate the proliferation of primary mouse splenocytes in vitro and increase adenosine triphosphate-generation capacity (ATP-GC) in cultured Caco 2 colon epithelial cells in vitro. Interestingly, oral administration of DS and RS (but not XYS, at 3 and 6 g/kg/day × 3 consecutive days) was found to stimulate the proliferation of splenocytes ex vivo at 24 h post-treatment in mice. Similarly, DS and RS (but not XYS) increased the ATP-GC of mitochondrial fractions isolated from a small segment of mouse intestine at 48 h post-treatment. This observation is consistent with the meridian tropism of the pharmacological action of “Shen”, i.e. , the accessibility of DS and RS (but not XYS) to the “Spleen” meridian. The comparison between the results obtained from in vitro and in vivo/ex vivo bioassays may offer a potential method for assessing meridian tropism in Chinese herbs.