Analysis of bronchoalveolar lavage fluid from bleomycin-induced pulmonary fibrosis in hamsters

Abstract

The purpose of this study was to analyze the cellular and noncellular components of bronchoalveolar lavage fluid (BALF) at varying times during the development of pulmonary fibrosis induced by bleomycin. Hamsters were killed and lavaged in situ following the administration of a single intratracheal injection of 1 unit of bleomycin or an equivalent volume of sterile isotonic saline. The results show that the total cell counts in the BALF of belomycin-treated hamsters, as compared with controls, were increased 7.7, 4.4, 2.4, 1.6, and 1.9-fold at 2, 4, 7, 14, and 21 days after treatment, respectively. The predominant cell types in the BALF of control animals were macrophages which constituted 84% of the total cells, followed by lymphocytes, 11%. The predominant cell types in the BALF of bleomycin-treated animals were polymorphonuclear leukocytes (PMN) which constituted 65% at two days and approximately 50% of the total at 4, 7, and 14 days; at 21 days macrophages were the predominant cell type constituting 50%, followed ty lymphocytes at 30%. However, the total number of lymphocytes was not increased at 21 days compared to previous times. The noncellular protein content of BALF from bleomycin-treated hamsters, an index of pulmonary vascular permeability, was increased to 224, 559, 637, and 270% of control (2.7 mg/lung) at 2, 4, 7, and 14 days after treatment, respectively, and returned to control levels at 21 days. The acid phosphatase activity in the supernatant of BALF of bleomycin-treated animals was significantly increased to 181, 181, 199, 176, and 125% of control (258 units/lung) at 2, 4, 7, 14, and 21 days, respectively. β-Glucuronidase activity in the supernatant of BALF of control hamsters was 64 units/lung, whereas in bleomycin-treated animals the activity was significantly increased to 226 units/lung at two days and that 161 units/lung at four days after treatment. Histamine content in the supernatant of BALF of bleomycin-treated animals was increased from a control value of 28 ng/lung to 41, 41, 59, 45 ng/lung at 2, 4, 7, and 14 days after treatment, respectively. There was no difference in the total prostaglandin E (PGE) content of the BALF-supernatant between control and bleomycin-treated hamsters. The data presented in this report demonstrate that the release of lysosomal enzymes and histamine may play a significant role in the pathogenesis of bleomycin-induced lung damage.