Characterization of biliary conjugates of 4,4'-methylenedianiline in male versus female rats.

4,4'-Methylenedianiline (4,4'-diaminodiphenylmethane; DAPM) is an aromatic diamine used in the production of numerous polyurethane foams and epoxy resins. Previous studies in rats revealed that DAPM initially injures biliary epithelial cells of the liver, that the toxicity is greater in female than in male rats, and that the toxic metabolites of DAPM are excreted into bile. Since male and female rats exhibit differences in the expression of both phase I and phase II enzymes, our hypothesis was that female rats either metabolize DAPM to more toxic metabolites or have a decreased capacity to conjugate metabolites to less toxic intermediates.

Effects of methylenedianiline on tight junction permeability of biliary epithelial cells in vivo and in vitro.

Methylenedianiline (DAPM) is considered a cholangiodestructive toxicant in vivo. Increases in biliary inorganic phosphate (P(i)) and glucose occur prior to biliary epithelial cell (BEC) injury, which could be due to increased paracellular permeability and/or impairment of P(i) and glucose uptake by BEC. To evaluate these possibilities, we induced mild injury [loss of BEC from major bile ducts (6 h), ultrastructural alterations in BEC mitochondria and Golgi cisternae (3 h), and striking increases in biliary P(i) and glucose (3-6 h)] with 25 mg DAPM/kg and then assessed temporal alterations in tight junction (TJ) permeability by measuring bile to plasma (B:P) ratios of [(3)H]-inulin.

Mitochondrial dysfunction occurs before transport or tight junction deficits in biliary epithelial cells exposed to bile from methylenedianiline-treated rats.

Methylenedianiline (DAPM) rapidly injures biliary epithelial cells (BEC) in vivo. Prior to evident BEC injury, biliary glucose and inorganic phosphate appreciably rise, which could stem from loosened tight junctions (TJ). Concurrently, ultrastructural abnormalities in BEC mitochondria of DAPM-treated animals are observed, suggesting other impairments.

Vascular medial hyperplasia following chronic, intermittent exposure to 4,4'-methylenedianiline.

4,4'-Methylenedianiline (DAPM) is an aromatic amine used in the synthesis of polyurethanes and epoxy resins. Acute exposure to DAPM produces hepatobiliary toxicity in humans as well as animal models. However, the toxic effects of intermittent DAPM exposure have not been explored.

Glutathione depletion exacerbates methylenedianiline toxicity to biliary epithelial cells and hepatocytes in rats.

Methylenedianiline (DAPM) initially injures epithelial cells of major bile ducts, which is followed by cholestasis, cholangitis, and hepatocellular damage. This pattern of biliary injury resembles that produced by alpha-naphthylisothiocyanate (ANIT), a classic bile duct toxicant. Our goal was to determine whether prior depletion of hepatic total glutathione (GSx), a condition reported to protect against biliary tract injury by ANIT, would also protect against DAPM-induced bile duct injury.