EXPERIMENTAL SILICOSIS .2. LONG-TERM EFFECTS OF INTRATRACHEALLY INSTILLED QUARTZ ON COLLAGEN-METABOLISM AND MORPHOLOGIC CHARACTERISTICS OF RAT LUNGS

  • 1 January 1983
    • journal article
    • research article
    • Vol. 110  (1) , 30-41
Abstract
Rats received intratracheal instillations of 50 mg silica (quartz, 0.5 .mu. particles). One, 2, 4, 5, 6, 9 and 12 mo. later, the lungs were evaluated histologically and by various biochemical measurements. The lung content of protein, Pro and Hyp (collagen) were quantitated, as were the synthesis rates of lung collagen and the total lung protein (evaluated with lung minces in vitro). The ratio of newly synthesized and of total lung type 1 to type 3 collagen was also determined. These experiments were performed in parallel on rats free of chronic respiratory disease and a strain of conventional animals. The excess collagen deposited in granulomas and/or silicotic nodules as part of the fibrotic response of the lung was similar to normal lung collagen with respect to relative ratios of types 1 and 3 present, in contrast to the response of the lung to oxidant pneumotoxins. The response of the lung to silica continued for at least 1 yr. 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, mature silicotic nodules and areas of alveolar lipoproteinosis associated with interstitial pneumonitis. Even 1 yr after instillation of silica areas of granulomas, silicotic nodules and alveolar lipoproteinosis were observed in most lungs.