In vitroanalysis of insoluble salt formation mechanism associated with Mg corrosion-variations depending on the diffusion environment in model tissue.

Magnesium (Mg) alloys have attracted attention as biodegradable metals, but the details of their corrosion behavior under biological environment have not been elucidated. Previous studies have suggested that diffusion through blood flow may influence Mg corrosion. Therefore, to understand the degradation behaviors of Mg, we analyzed insoluble salt precipitation associated with Mg corrosion in model tissue with different diffusion rates. A pure Mg specimen was immersed into a model tissue prepared with cell culture medium supplemented by a thickener at a different concentration (0.2%-0.5%) to form the gel. Micro-focus x-ray computed tomography of the gel was performed to observe gas cavity formation around the specimen. The insoluble salt layer formed on the specimen surface were analyzed by scanning electron microscopy with energy-dispersive x-ray spectroscopy, and Raman spectroscopy. As results, gas cavity formation was observed for all specimens. At day 7, the gas cavity volume was the highest at 0.5% thickener gel followed by 0.3% thickener gel. The insoluble salts were classified into three types based on their morphology; plate-like, granular-like, and crater-like salts. The crater-like salts were observed to cover 16.8 ± 3.9% of the specimen surface immersed in the 0.5% thickener gel, at the specimen area contacted to the gas cavity. The crater-like salts were composed by Mg hydroxide and carbonate from the deepest to the top layer. In plate-like or granular-like salts, Mg carbonate was formed in the deepest layer, but phosphates and carbonates, mainly containing calcium not Mg, were formed on the surface layer. In conclusion, the increase in the thickener concentration increased the gas cavity volume contacting to the specimen surface, resulting in the increase in precipitation of Mg hydroxide and carbonate, composing crater-like salts. Mg hydroxide and carbonate precipitation suggests the local increase in OH-concentration, which may be attributed to the decrease in diffusion rate.

Characterization of release profile of ornithine carbamoyltransferase from primary rat hepatocytes treated with hepatotoxic drugs: Implications for its unique potential as a drug-induced liver injury biomarker.

Ornithine carbamoyltransferase (OCT) is a mitochondrial protein expressed primarily in the liver. It has been shown that, like alanine aminotransferase (ALT), OCT is released from damaged hepatocytes in rats and humans, which has given rise to the possibility that OCT might provide a diagnostic biomarker of various forms of liver damage, including drug-induced liver injury (DILI). However, OCT release characteristics in DILI, as well as their diagnostic advantages, remain elusive. Therefore, this study aimed at clarifying whether and how OCT is released from rat primary hepatocytes in vitro using seven potentially hepatotoxic drugs. The results showed that OCT releases from damaged hepatocytes were observed for all tested drugs, and that those releases were not associated with mitochondrial membrane proteins. It should be underscored that the release dynamics were significantly larger than those of ALT. Furthermore, unlike ALT, the maximum OCT release levels showed differences depending on the drug being tested, suggesting that OCT release was susceptible to toxicity mechanisms. Taken together, these unique release characteristics highlight the possibility that OCT could provide a promising DILI biomarker that might contribute not only to diagnostic accuracy improvements, but also to a better understanding of toxicity types in clinical and drug development settings.