Morphologic and biochemical effects of intratracheally administered oil shale in rats

Young adult rats were given three weekly intratracheal instillations of 30 mg of raw oil shale or spent oil shale suspended in 1.0 ml sterile physiological saline. Positive control groups received similar instillations of 30 mg or 5 mg of quartz. Animals were sacrificed and tissue samples taken for histopathology and biochemical analyses at 3 weeks, 7 weeks, 4 months, and 8 months following the first instillation. Rats exposed to raw shale, spent shale or quartz had increased lung weights compared with controls. Microscopically, all exposed groups developed granulomatous pneumonia and alveolar lipoproteinosis; pulmonary fibrosis was most severe in the quartz-exposed groups and progressed with time in these groups. Total amounts of pulmonary hydroxyproline, prolyl hydroxylase, total protein, and lipid phosphate were increased in shale or quartz-exposed groups; however, concentration of these substances on a per gram of lung tissue basis was not different from control groups.