Preliminary observation of the migration of sodium fluorescein along meridians in the limbs of mini-pigs

Meridians are a core concept in traditional Chinese medicine (TCM) theory. It has been shown in many previous studies that meridians exist in the interstitium, the space through which interstitial fluids flow. Sodium fluorescein (SF) is a small, fluorescent, hydrophilic molecule. SF was injected into the low impedance points (LIPs) or the high impedance points (HIPs) on the limbs of healthy mini-pigs, as determined by a low impedance meridian locator (WQ6F30). Migration tracks were scanned by a digital camera (Canon 5D2) with a narrow band filter and colored flash lamps prior to and after SF injection. The relationships between superficial veins and SF tracks were analyzed using a projection vein finder (V800P). Tissues were frozen on dry ice, and the distribution of SF in the transverse sections of SF tracks was observed. Results reliably showed that seven migrating tracks along the low impedance line along meridians (LILM) were found when SF was injected at LIPs, three of which were on the outside of forelimb, three of which were on the inside of forelimb, and one of which was on the inside of hind limb. The average length of these migration tracks was 5.13 cm. The migration tracks were 81.4% consistent with LILM, while no overlap was observed with veins. The shape of injected SF in the transverse sections was similar to an inverted triangle, and distributed in the muscle gap. No linear migration was observed when SF was injected at HIP, and the shapes of injected SF were nearly round by local diffusion. The length, width and length-width ratio of SF shapes between injections at LIPs and HIPs were significantly different (P<0.01). These results imply that the concept of the meridian in TCM may be an unknown interstitial channel.