Correlative morphological and biochemical studies on monocrotaline-induced pulmonary alterations in rats

A single s.c. injection of 60 mg/kg of monocrotaline to rats induced pulmonary alterations characterized by hyaline thrombi of capillaries and arterioles, focal necrosis of alveolar walls, and medial thickening and intimal hyalinosis of arteries. Such pathological alterations became apparent 7 days after injection and thereafter progressively developed with the passage of time. Histometrical examination revealed a reduction of the alveolar surface area in a unit volume of lung tissue in these rats. Biochemically, lung angiotensin-converting enzyme activity was estimated to have reduced in parallel with the development of pulmonary alterations while plasma angiotensin-converting enzyme activity was unchanged throughout the experimental period.