DiI staining of fine branches of Bonghan ducts on surface of rat abdominal organs.

Novel thread-like structures and corpuscles, designated Bonghan ducts (BHDs) and corpuscles (BHCs), are known to form a system of networked channels. Here, we tested the effectiveness of a fluorescent carbocyanine dye, DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate), in staining BHDs and BHCs. DiI solution was infused into a BHC on the surface of a rat abdominal organ at a steady rate and the resulting labeling of neighboring BHCs connected via BHDs was examined, as identified by the red fluorescence of DiI. BHDs diameters tapered away from BHCs and formed tree-like branches with fine arborizations embedded in the membranous tissues at their terminal parts. In the proximal parts, DiI fluorescence appeared as continuous lines within BHDs, but a large portion of BHDs remained unstained. In the distal parts of BHDs, discontinuous elongated DiI microparticles were identified along the sinuses within BHDs. The results showed that inner spaces within the BHDs allowed DiI to flow and that BHDs have tree-like branches and terminal arborizations. In conclusion, DiI can be used in visualizing BHDs fine structures.

Proteomic analysis for tissues and liquid from bonghan ducts on rabbit intestinal surfaces.

Research on the Bonghan system has recently prompted great interest in the theory proposed by Bong Han Kimin in the early 1960s. In order to study the biochemical characteristics of the Bonghan system, we analyzed Bonghan ducts (BHD) on the surface of rabbit intestines and characterized the liquid in the BHD at the level of the proteome. Proteomic analysis was performed using nano LC-ESI MS/MS. Using a solution digestion technique, we identified 70 different proteins in the liquid of the BHD. We used gel-based digestion to analyze the BHD itself and our results showed the presence of 207 proteins. We used these proteins to analyze gene ontology (GO) to yield insights into biological processes, molecular functions and cellular compartmentalization. Remarkably, GO clustering showed high concentrations of proteins involved in metabolism. These proteins are not usually found in blood, lymph or blood vessels, and thus can be useful for characterizing BHD. It is worth studying their association with stem cells, especially mesenchymal stem cells, cancer cells and myeloid cells.