Hepatotoxic Effects of Sub-Chronic Nitrocellulose Thinner Vapour Exposure and Incomplete Recovery Following Withdrawal in Male Wistar Rat

Background: Nitrocellulose thinner is a widely used industrial solvent mixture with recognized toxicological risks. Occupational exposure, particularly among painters and other industrial workers, is common; however, the extent of hepatic recovery following prolonged inhalation exposure remains poorly understood. This study evaluated the hepatotoxic effects of subchronic nitrocellulose thinner vapor (NCTV) inhalation and the degree of hepatic recovery following withdrawal in male Wistar rats.

Methods: Twenty-four adult male Wistar rats were randomly allocated into three groups (n = 8 per group): a control group, an NCTV exposure group (4 hours/day for 90 consecutive days), and a withdrawal group exposed to NCTV for 90 days followed by a 90-day recovery period without further exposure. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), total and conjugated bilirubin, total protein, albumin, and globulin were measured using standard colorimetric methods. The albumin-to-globulin (A/G) ratio was calculated, and liver tissues were examined histologically using hematoxylin and eosin staining.

Results: Sub-chronic NCTV inhalation significantly increased serum ALT, AST, ALP, and total bilirubin levels (p < 0.05) while significantly reducing total protein and globulin concentrations, resulting in an increased A/G ratio. Histopathological examination demonstrated vascular congestion, sinusoidal dilatation, inflammatory cell infiltration, and hepatocellular swelling. Following the 90-day withdrawal period, serum ALT, ALP, and total bilirubin levels declined significantly and approached control values. However, AST remained significantly elevated (p < 0.05), albumin concentrations decreased significantly compared with both the control and exposure groups, resulting in a marked reduction in the A/G ratio (0.43 ± 0.06), and conjugated bilirubin remained significantly higher than in controls (p < 0.05). Histological examination revealed only partial recovery, with persistent vascular congestion and mild hepatic architectural abnormalities.

Conclusion: Sub-chronic inhalation of nitrocellulose thinner vapor induces significant hepatotoxicity in male Wistar rats. Although withdrawal leads to partial biochemical and histological recovery, persistent alterations in liver function biomarkers and hepatic architecture suggest incomplete hepatic recovery following prolonged exposure. These findings underscore the potential for long-term liver injury associated with chronic occupational exposure and highlight the importance of preventive measures and adequate recovery periods.