Background: aluminum is the third most common element in the earth's crust and is about 8% of its total mineral components. It is widely used in antacid drugs, food additives and tooth pastes. Moreover, it is added to the drinking water for purification purposes. It is also the metal of choice in making several household cookware and storage utensils despite its toxic effects.
      Aim of the work: this study aimedto describe the histological changes which occurred in liver of rats exposed to aluminum and also to clarify whether those changes were related to the age of the experimental animals or not.
       Material and methods: 32 male albino rats were used in this study, 16 adults and they were weighing 150-180 gm and 16 senile and they were weighing 400-450 gm. Group I: was consisted of 16 adult male rats. This group was categorized into two equal subgroups; subgroup IA and subgroup IB. Group II: was consisted of 16 senile male rats. This group was categorized into two equal subgroups; subgroup IIA and sub group IIB. Subgroups IA and IIA were served as control and received distilled water. Subgroups IB and IIB received aluminum chloride in a dose of 475 mg/kg body weight by gastric gavage once daily for three weeks. At the end of the experiment, liver specimens were collected, processed for paraffin blocks and semithin sections and examined by light microscope.
      Results: liver sections obtained from adult rats received aluminum chloride showed disrupted and discontinuous liver capsule, disorganized hepatic architecture, affection of the hepatocytes especially those under the liver capsule which had small darkly stained nuclei and dilated, distorted and slightly congested central veins. Most of the blood sinusoids appeared either narrow and obliterated or congested. The portal triads showed vascular congestion and dilatation, proliferation of the bile ducts with slight increase in the collagen deposition around the portal triads. Sporadic positive PAS reaction within the cytoplasm of the hepatocytes was also noticed in liver sections stained with PAS stain. Semithin sections stained with toluidine blue showed well circumscribed vacuoles of different sizes inside and outside the hepatocytes. On the other hand, liver sections obtained from senile rats received aluminum chloride showed the same previous changes that occurred in the adult group, but they were exaggerated and there were additional changes such as the presence of irregular homogenous materials and tiny vacuoles in the cytoplasm of most of the hepatocytes.
        Conclusion: oral administration of aluminum chloride in rats resulted in degenerations in the liver and that was conclusive of toxic hepatitis. These changes were exaggerated among the senile rats which proved that senile rats are more susceptible to the hepatoxicity induced by aluminum. Therefore, it is advised to create awareness among people especially the senile ones about the hazards of extensive use of aluminum.