effect of oral administration of formadehyde on the liver of the albino rat: an electron microscopic study

ABSTRACT

Formaldehyde is an electrophilic molecule able to crosslink DNA and protein which leads to its claim for cytotoxicity and carcinogenicity. It is used as a disinfectant, antiseptic, in the manufacture of plastic and resins and in cheese production to give the cheese the firm consistency. Previous studies have focused on the direct acute harmful effects of formaldehyde on the skin, eye and respiratory system while less efforts have been made to evaluate its possible harmful effects on different body systems after long period of oral administration of a reasonably low dose. The possible toxic effect of formalin [40% solution of formaldehyde in water] on the ultrastructure of the liver of albino rat has been evaluated in the current study as the liver is the main site for formaldehyde metabolism in the body. Two groups of albino rats of 10 animals each were used where the first group received 25 mg/kg/day of formalin orally by gavages for three weeks while the second group received an equivalent volume of distilled water orally by gavages and used as control. The results showed that formalin markedly affected liver ultrastructure at the levels of hepatocytes, intrahepatic biliary system and portal tracts. Hepatocytes showed nuclear degeneration, mitochondrial degeneration, shortening and fragmentation of rough endoplasmic reticulum and peroxisomal alteration. Intrahepatic biliary system affection appeared in the form of dilatation of the bile canaliculi with shortening or complete loss of microvilli and degeneration of the covering epithelium of bile ductules. Infiltration of the portal tracts with neutrophils, lymphocytes and plasma cells were also observed which indicated an inflammatory process in the portal tract. The results, which suggest a marked toxic effect of formalin on the liver after oral administration of small doses for a long period, have been discussed. A recommendation for properly avoiding the harmful effect of this chemical substance has been offered especially the proper application of its prohibition in cheese and dairy production