EXPERIMENTAL SILICOSIS .1. ACUTE EFFECTS OF INTRATRACHEALLY INSTILLED QUARTZ ON COLLAGEN-METABOLISM AND MORPHOLOGIC CHARACTERISTICS OF RAT LUNGS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 107  (2) , 176-185
Abstract
Rats were intratracheally instilled with 50 mg of silica as quartz (0.5 .mu.m particles) at day 0. One and 2 wk later, lungs were evaluated histologically and by a variety of biochemical measurements. Protein, proline and hydroxyproline content (as an index of total lung collagen) were quantitated, as were the lung collagen synthesis rate and the total lung protein biosynthesis rate (evaluated with lung minces in vitro). The ratio of newly synthesized type 1/type 3 collagen was determined, as was the same ratio for total lung collagen. These experiments were performed in parallel on chronic respiratory disease-free rats and in a strain of conventional animals. Changes in lung structure and composition were seen as early as 1 wk, the earliest time point studied, after intratracheal instillation of 50 mg quartz. Morphologic changes during the first 2 wk were consistent with biochemical changes. There were essentially no differences in the response of chronic respiratory disease-free Sprague-Dawley and conventional Wistar rats to intratracheally instilled silica. Both strains of rats developed silica-containing granulomas which ultimately developed into silicotic nodules and areas of alveolar lipoproteinosis associated with interstitial pneumonitis.