Acute Toxicity in the Rat Lung Induced by Intratracheal Instillation of Glycolic Acid

Abstract

Background/Aim: Inhalation toxicity tests of glycolic acid, which is used in many household products, have been reported, but the pulmonary toxicity of glycolic acid has not been confirmed. Here, the lung damage caused by glycolic acid was investigated in rats. Materials and Methods: An intratracheal instillation test was performed with glycolic acid in male rats. Bronchoalveolar lavage fluid (BALF) and histopathological analysis were conducted to identify the pulmonary toxicities. Results: Intratracheal instillation of glycolic acid caused weight loss in animals and increased the content of lactate dehydrogenase, total protein, polymorphonuclear neutrophils, and inflammatory cytokines in BALF. In addition, pulmonary edema, alveolar/interstitial inflammation, and necrosis and desquamation of bronchial/bronchiolar epithelia were confirmed via histopathological examination. Conclusion: Exposure to glycolic acid can be harmful and toxic to the lungs.Glycolic acid, also known as hydroxyacetic acid, is widely used in the cosmetic, textile, food, and pharmaceutical industries (1-3). The global glycolic acid market is expected to grow gradually every year (4). This means people will be more exposed to glycolic acid, via skin contact, oral intake, or inhalation. Workers dealing with glycolic acid, in particular, are more likely to be exposed to it (5).Glycolic acid was assigned to the hazard statement H332 for acute inhalation toxicity (6). The inhalation LC 50 (4-h exposure) of glycolic acid for rats has been reported to be 7.1 mg/l, and the no observed adverse effect concentration values were 0.16 mg/l and 0.05 mg/l or higher for 14-( 7) and 28-day inhalation exposure (8), respectively.There are many differences between humans and rodents. One of them is that rodents are obligatory nasal breathers, whereas humans are oronasal breathers. This means that the lower respiratory tract of humans may be more exposed to substances than that of rodents (9, 10). Animal inhalation experiments with glycolic acid have been performed, but the damage to the lower respiratory tract or the toxic effects derived from acute inhalation have not been clearly identified. Therefore, we conducted intratracheal instillation experiments to confirm the pulmonary toxicities of glycolic acid in Sprague-Dawley rats. Materials and MethodsReagents. Glycolic acid (Cas no. 79-14-1) was obtained from Sigma-Aldrich (St. Louis, MO, USA). Dulbecco's Phosphate Buffered Saline (DPBS) was purchased from Lonza (Basel, Switzerland). 10% neutral buffered formalin was purchased from BBC Biochemical (McKinney, TX, USA). Isoflurane was purchased from Piramal Critical Care (Bethlehem, PA, USA).Animals and treatments. The animal study was approved by the Institutional Animal Care and Use Committee (IACUC) of the National Institute of Environmental Research (NIER) (Republic of Korea) and an IACUC-approved test protocol was followed. Male Sprague-Dawley (6-week-old) rats were purchased from Orient Bio Inc., (Seongnam, Republic of Korea). Animals were housed at room tem...