Disintegration of lung peroxisomes during differentiation of type II cells to type I cells in butylated hydroxytoluene-administered mice.

Ultrastructural and cytochemical changes in peroxisomes of Type II alveolar cells were investigated in butylated hydroxytoluene (BHT)-administered mouse lungs. Male mice were given a single injection of BHT (400 mg/kg, ip) and sacrificed 1 to 7 days later. By means of tracheal infusion, lungs were fixed with a 2% glutaraldehyde or half-strength Karnovsky solution. Type I epithelium was selectively destroyed by BHT and was replaced by cuboidal Type II cells. Type II cells proliferated and some became squamous, extended their cytoplasm, and might differentiate into Type I cells (Hirai, Witschi, and Côté (1977) Exp. Mol. Pathol. 27, 295-308). Peroxisomes, Type II cell constituents, were clustered around and continuous with endoplasmic reticulum. The shape of the peroxisomes became indistinct after Type I cell injury by BHT. Also the density of the matrix was reduced in proportion to the reduction in the peroxidatic activity of catalase. These changes were accompanied by a decrease in the number of peroxisomes. New pinocytotic vesicles, one of the Type I cell characteristics, were generated at the apical and basal cell surfaces. Therefore, these cells had characteristics intermediate between Type I and Type II cells. These findings may indicate further evidence of the origin of Type I cells from Type II cells.