SUBACUTE IMMUNOTOXICITY STUDY OF FORMALDEHYDE IN MALE-RATS

Immune functions were examined in male rats following 28 day oral admi nistration of formaldehyde by gastric tube at dose levels of 0, 20, 40 , and 80 mg/kg. Routine parameters examined included hematology, clini cal chemistry, and body, thymus, kidney, and liver weights. In additio n, cellularity of spleen and lymph nodes, histology of spleen, thymus, lymph nodes, liver, kidney, small and large intestines, and histochem istry of spleen and lymph nodes were evaluated. Immune parameters eval uated included serum hemagglutinin antibody response; antibody plaque forming cell response to sheep erythrocytes (lymphocyte-dependent anti gen); microbicidal activity of Candida albicans; and phagocytic activi ty by adhesion of microspheric hydrophylic synthetic particles to leuk ocyte cell membrane. Body weights were slightly decreased at high dose level (80 mg/kg). The difference was significant when compared to the controls. The lymph node weights were significantly increased in rats receiving formaldehyde. The cellularity of lymphoid organs was not in fluenced after 28 day exposure to formaldehyde. Oral administration of formaldehyde to rats resulted in dose-dependent reduction of antibody responses (IgG+IgM) at doses of 20, 40, and 80 mg/kg. However, there was no significant reduction of the spleen cells producing IgM antibod ies in exposed rats. With the exception of the activity of PMN + monoc ytes, the microbicidal activity of cells which phagocytized Candida al bicans and phagocytic activity of blood leukocyte cells were not signi ficantly decreased. In comparison to controls, the hepatocytes of the exposed animals had increased cytoplasmic vacuolization. Histochemistr y revealed narrowing of the thymus- dependent zone in the spleen. In a ddition, channels across the marginal zone were frequently observed. T hese channels probably allow direct migration of lymphocytes from the thymus dependent zone into the red pulp spleen.