Effect of toluene exposure on pulmonary alveolar structure of adult male albino rats. toxicological and histological study

ABSTRACT

Toluene is an aromatic volatile solvent included in widely distributed commercial products like j gasoline, paints, glues and thinners. It is largely abused as a neurostimulant agent in adolescents and young adults in low socioeconomic classes. The present work aimed at investigating the effect of long-term toluene administration on the histological structure of pulmonary alveoli of adult male albino rats. It was further extended to evaluate the possibility of recovery after toluene withdrawal. Thirty adult male albino rats [100-120 g] were randomly categorized among 3 equal groups; group I [control group]. Group II rats were orally intubated with 10 mI/kg body weight of toluene in corn oil at a dose of 650 mg/kg/day, five days per week for 8 successive weeks. Group III [withdrawal group] rats were subjected to oral ivluene administration in a similar way to group II and for the same period. Then, they were kept free from toluene exposure for the next 4 weeks to test for spontaneous recovery. By the end of the experimental periods, blood samples were collected from all animals for estimation of blood toluene levels by gas chromatography. Then, the rats were sacrificed by decapitation after anaesthesia. Lung specimens were taken from all animals and processed for light microscopic examination using H and E stain, as well as transmission electron microscopic examination. Toluene administration in group II rats resulted in an evident increased in blood toluene levels as compared to the control group. Histologically, toluene exposure resulted in evident alteration of the pulmonary alveolar architecture with focal areas of collapsed alveoli, marked thickening of the inter-alveolar septa along with peribronchiolar and perivascitlar cellular infiltration as well as vascular congestion. Ultrastructurally, type II pneumocytes formed the predominant lining cells of many alveoli and revealed small dense nuclei, and numerous wicuoles, while others exhibited rarfied cytoplasm and empty lame lIar bodies. Increased deposition of collagen and elastic fibers in the inter-alveolar septa was depicted as well. After 4 weeks of toluene withdrawal [group III], an evident decrease in blood toluene levels was enco4nte red. Nevertheless, it was still high in relation to the control levels. Histologically, only mild amelioration of the alveolar lesions was revealed. Some alveoli were still collapsed. The inter-alveolar septa were moderately thickened with increased collagen deposition. Some morphological changes of type Ilpneumocytes were still depicted. Long-term exposure to toluene has the potential to endanger the pulinonaty alveolar structure. Therefore, laws and penalties should be legislated to prohibit the abuse of such substance. Public health efforts are recommended to raise the awareness about its hazards particularly among high risk population