Health Assessment Document for Diesel Emissions - NSCEP | US ...

1 serum enzymes in the control versus the exposed female rats appear to be a random event among
2 these aged subjects. The incidence of age-related disease, such as mononuclear cell leukemia,
3 can markedly affect such enzyme levels, seriously compromising the usefulness of a comparison
4 to historical controls. The serum sodium values of 144 versus 148 mmol/L in control and
5 exposed rats, respectively, although statistically different, would have no biological import.
6 The increased serum enzyme activities, aJkaline phosphatase, SGOT, SGPT, garnma-
7 glutamyl transpeptidase, and decreased cholinesterase activity suggest an impaired liver;
8 however, such an impairment was not established histopathologically (Heinrich et al., 1982;
9 Research Committee for HERP Studies, 1988; Brightwell et al., 1986). The increased urea
10 nitrogen, electrolyte levels, and gamma globulin concentration and reduction in total blood
11 proteins are indicative of impaired kidney function. Again there was no histopathological con:fir-
12 mation of impaired kidneys in these studies.
13 Clinical chemistry studies suggest impairment of both liver and kidney functions in rats
14 and hamsters chronically exposed to high concentrations of diesel exhaust. The absence of
15 histopathological confirmation, the appearance of such effects near the end of the lifespan of the
16 laboratory animal, and the failure to find such biochemical changes in cats exposed to a higher
17 dose, however, tend to discredit the probability of hepatic and renal hazards to humans exposed
18 at atmospheric levels of diesel exhaust.
19
20 5.1.2.3.9. Effects on microsomal enzymes.· Several studies have examined the effects of diesel
21 exhaust exposure on microsomal enzymes associated with the metabolism and possible
22 activation of xenobiotics, especially polynuclear aromatic hydrocarbons. These studies are
23 summarized in Table 5-12. Lee et al. ( 1980) measured the activities' of aryl hydrocarbon
24 hydroxylase (AHH) and epoxide hydrase (EH) in liver, lung, testis, and prostate gland of adult
25 male rats exposed to 6.32 mg/m 3 DPM 20 h/day for 42 days, Maximal significant AHH activities
26 (pmol/min/mg microsomal protein)occurred at different times during the exposure period, and
27 differences between controls and exposed rats, respectively, were as follows: prostate
28 0.29 versus 1.31, lung 3.67 versus 5.11, and liver 113.9 versus 164.0. There was no difference in
29 AHH activity in the testis between exposed and control rats. Epoxide hydrase activity was not
30 significantly different from control values for any of the organs tested.
31 Pepelko and Peirano (1983) found no statistical differences in liver microsomal
32 cytochrome P448-450 levels and liver microsomal AHH between coritrol and diesel-exposed
33 mice either at 6 and 8 mo of exposure. Small differences were noted in the lung microsomal
34 AHH activities, but these were believed to be artifactual differences, due to increases in
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