Effects of nitrogen dioxide (NO
2) exposure on prostacyclin (PGIP
2) synthesis in the rat lung and thromboxane A
2 (TXA
2) synthesis in the platelets were studied. Male Wistar rats were exposed to 10 ppm NO
2 for 1, 3, 5, 7 and 14 days. PGI
2 synthesizing activity of homogenized lung decreased. The damage of PGI
2 synthesizing activity reaches its maximum at 3 days. At 14 days, PGI
2 synthesizing activity returned to the normal level. The activity of PGI
2 synthetase decreased significantly. The formation of lipid peroxides due to NO
2 exposure may cause the depression of PGI
2 synthesizing activity of lung. On the other hand, platelet TXA
2 synthesizing activity increased. This increased TXA
2 synthesizing activity lasted at least till 3 days. Then, it returned to the normal level. The counts of platelet were decreased significantly by 1, 3, 5 and 7 days NO
2 exposure. Then the decreased counts of platelet returned to the normal level at 14 days NO
2 exposure. These results indicate that the depression of PGI
2 synthesizing activity lung by NO
2 exposure cause an increase in TXA
2 synthesizing activity of platelets. It may contribute to induce platelet aggregation and to the observed decrease in the number of platelets during NO
2 exposure.
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