Abstract
To detect the fundamental metabolic pathway of periodontal ligament and dental pulp, 14C-labelled succinate was used as a tracer. The sliced periodontal ligament and pulp were suspended in Krebs-Ringer phosphate buffer and incubated with succinate-1, 4-14C, following which, the glycosaminoglycans (GAGs) were subjected to electrophoresis and cation exchange chromatography.
The fraction extracted with 0.16 and 1.0 M NaCl showed that the solubility and relative proportion of proteoglycans and GAGs were distinct in the periodontal ligament and dental pulp. The highest level of radioactivity was detected in the newly synthesized hyaluronic acid, using electrophoresis, with no detectable radioactivity found in the dermatan sulfate or chondroitin-4, and-6 sulfate. After hydrolysis of GAGs, followed by Aminex A-6 ion exchange chromatography, radioactivity from succinate-1, 4-14C was mainly found in the hexuronate portion of the hyaluronate. However, traces of radioactvity were detected in the glucosamine and in addition, the 3H-glucosamine was incorporated in the GAGs of the periodontal ligament and dental pulp when introduced into the incubation system.
Therefore, succinate-1, 4-14C added to the incubation medium was converted into intermediates of the TCA cycle and then through gluconeogenesis, via phosphoenolpyruvate, the fructose-6-phosphate was synthesized with radioactive 14C. A reasonable hypothesis is that since glucosephosphate isomerase activity seems to be higher than that of hexose phosphate amino transferase, it would appear that the 14C labelled UDP-glucuronate from the succinate-1, 4-14C is incorporated in the newly synthesized hyaluronic acid.
