Effects of nitrate and nitrite, chemical intermediates of inhaled nitrogen dioxide, on membrane components of red blood cells of rats

Abstract

Rat blood was incubated at 37°C for 60 min with either NaNO 3 or NaNO 2 to examine the relationship between the decrease in the hexose content and Ca 2+,Mg 2+-ATPase activity of red cell membranes, and NO 3 − and NO 2 −. The hexose content decreased depending on the NaNO 2 concentration up to 100 μ m reaching 76% ( p < 0.05) of the control value. NaNO 3 had little effect on the hexose content. On the other hand, the Ca 2+,Mg 2+-ATPase activity decreased depending on the NaNO 3 concentration up to 200 μ m, where the activity reached 75% ( p < 0.01) of the control value. The effect of NaNO 2 on this activity was smaller than that of NaNO 3. The sialic acid content and the Na +,K +-ATPase activity did not show significant alterations by incubation with NaNO 2 and NaNO 3 at below 100 μ m. To examine the in vivo effects of NO 2 − and NO 3 −, 50 m m NaNO 3 was intravenously injected into rats five times at hourly intervals (dose: 1.0 ml/kg body weight), and blood was collected 1 hr after the last injection. The activities of Ca 2+,Mg 2+- and Na +,K +-ATPases of red cell membranes were decreased to 68% ( p < 0.05) and 80% of the control value, respectively. Reduction by injection of 50 m m NaNO 2 was smaller than that by 50 m m NaNO 3. The results show that the hexose content and the Ca 2+,Mg 2+-ATPase activity of red cell membranes were decreased by NO x − that increased in the blood during short-term exposure of rats to NO 2.