Histometric changes in connective fibers of the lung following paraquat administration in rats

Pulmonary fibrosis induction by paraquat was studied histometrically using an image analyzer. Rats were given a subcutaneous injection of paraquat (7 or 25 mg/kg) and autopsied 3, 6 or 9 days later. The percentage of the area of connective fibers per unit area, and lung prolyl hydroxylase activity, as a biochemical parameter, were measured. Rats treated with 25 mg/kg of paraquat showed an increase in the percentage of the area of the connective fibers per unit area and also an increase in lung prolyl hydroxylase activity 6 days later. Thus, pulmonary fibrosis was confirmed both morphologically and biochemically. It is concluded that histometric examination using an image analyzer provides a very accurate method for the evaluation of pulmonary fibrosis.