AbstractThere has been evidence that an acute exposure of laboratory animals to nitrogen dioxide (NO2) for a short period of time can cause marked inhibition of pulmonary PGDH activity. Since diesel exhaust contains NO2, this investigation was undertaken to determine the effect of long‐term exposure of guinea pigs and rats to diesel exhaust. The study involves measurement of PGDH activity in the lung tissue as obtained from these animals following exposure to 250 and 1500 μg m−3of diesel particles for various time periods in relation to the appropriate time‐matched controls. In guinea pigs, exposure for 6 weeks to 250 μg m−3of diesel exhaust seems to stimulate the PDGH activity about two‐fold in comparison to the time‐matched controls while, paradoxically, the exposure to 1500 μg m−3of diesel exhaust did not show any particular effect. The exposures to diesel exhaust for 12 weeks, as well as 24 weeks, seem to show concentration dependent lowering of PGDH activity as compared to the time‐matched controls. This study also documents the well‐known species difference in PGDH activity in that the rat shows much lower activity of this enzyme than the guinea pig. Because of undetectable enzyme activity in many samples, it has not been possible to draw any meaningful conclusion as to the effect of diesel exposure
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