Inhibitory characteristics of styrene & styrene oxide on Na+,K+ activated adenosine triphosphatase.

Styrene, an important ingredient of plastic, is reported to cause it neurotoxic effects through its important metabolite styrene oxide. Na+, K+ -ATPase (NKA), an important enzyme in the neurotransmission processes, is found to be inhibited by styrene (200 mg/kg) and styrene oxide (55 mg/Kg) by 15 and 45% respectively. Kinetic evaluations show that Km values, number of interaction sites and rate of reaction, with respect to K+ ions, decreased in styrene oxide treated NKA samples. However, high Km values of Na+ sites suggest for low affinity with respect to Na+ ions. Na+ and K+ ion activation, ATP hydrolysis and ouabain titration patterns indicate for a conformational change in NKA mainly due to styrene oxide.