The principal aim of the work is to determine possibilities of using a model system that in vitro registers changes in membrane functional activity as a toxicity biomarker of water media. Functional activity was evaluated according to the proton pump (K+, Mg2+-ATPase) activity of Nitellopsis obtusa cell membrane structures. 50 % inhibition of K+, Mg2+-ATPase activity (IC50) was measured in membrane preparations and sensitivity of both freshly isolated and frozen microsome fractions for xenobiotics was investigated. Sensitivity of frozen (-8 oC) microsomal fraction (49±17 μM, n=8) did not significantly (p=0.05) differ from that of freshly isolated one (37±31 μM, n=12), as confirmed by a reference procedure with CuSO4. Sensitivity of frozen microsomal fraction did not change while stored in a fridge for at least 40 days, moreover, the variability of the ATPase activity inhibition endpoint values was less in relation to freshly isolated microsomal fraction. Applying the above-described model systems (H+-ATPase inhibition and electrophysiological characteristics), toxicity of water media under different conditions and at different distances from pollution sources was evaluated in the environment.
Keywords: plasmalemma, phytotoxicity, Nitellopsis obtusa, heavy metals, K+, Mg2+-ATPase activity.