This study examined the urinary excretion of tetrodotoxin (TTX) modeled in a porcine renal proximal tubule epithelial cell line, LLC-PK1. Time course profiles of TTX excretion and reabsorption across the cell monolayers at 37 °C showed that the amount of TTX transported increased linearly for 60 min. However, at 4 °C, the amount of TTX transported was approximately 20% of the value at 37 °C. These results indicate that TTX transport is both a transcellular and carrier-mediated process. Using a transport inhibition assay in which cell monolayers were incubated with 50 µM TTX and 5 mM of a transport inhibitor at 37 °C for 30 min, urinary excretion was significantly reduced by probenecid, tetraethylammonium (TEA), l-carnitine, and cimetidine, slightly reduced by p-aminohippuric acid (PAH), and unaffected by 1-methyl-4-phenylpyridinium (MPP+), oxaliplatin, and cefalexin. Renal reabsorption was significantly reduced by PAH, but was unaffected by probenecid, TEA and l-carnitine. These findings indicate that TTX is primarily excreted by organic cation transporters (OCTs) and organic cation/carnitine transporters (OCTNs), partially transported by organic anion transporters (OATs) and multidrug resistance-associated proteins (MRPs), and negligibly transported by multidrug and toxic compound extrusion transporters (MATEs).
Hinoki cypress (Chamaecyparis obtusa) -lignophenol (p-cresol type, HCLC) has been directly synthesized from lignocellulosics through the phase-separation system composed of concentrated acids and phenols under mild conditions. Thermal responses of HCLC were estimated by FT -IR, GPC, UV-Vis, TMA, TG, DSC and 1 H-NMR. The HCLC annealed up to 180 °C have large molecular weight distribution estimated by GPC. The results showed both de-polymerization through the cleavage of unstable C 1 -aryl ethers and polymerization through attacks of adjacent phenolic units to resulting reactive points on C 1 occurred in the same time on the molecules. Although an exothermal peak of HCLC was• detected by DSC, HCLC annealed up to 200 °C, exothermal peaks were vanished with focusing of the Mw to about 4 000. These heat resistant materials with new conjugated structures, which were produced by eliminations of aliphatic hydroxyl groups, held recycle designs. In fact, HCLC annealed up to 300 °C, the Mw were focused to 1 000-2 500 by phenol switching under alkaline conditions at 140-170 °C. Thus annealed HCLC over 200 °C kept particular structures of lignophenol, especially both grafting p-cresol and C 2 -0-aryl type linkages without random thermal decompositions.
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