| dc.description.abstract | The effects of low level lead (Pb) exposure in culture for 3 days on the non-specific ATPase activity of rat C6 glioma cells was studied. Cells were incubated in media containing Pb acetate at a concentration of 10⁻⁶M, 10⁻⁵M, or 5 x 10⁻⁵M. Cells were harvested, the plasma membranes were isolated, and an ATPase assay was performed, with activity being determined at the end of incubation by the level of inorganic phosphate present in the assay solution. Significant changes were not seen in ATPase activity at any Pb concentration when the ATPase assays were performed with ATP at 3mM; the average difference between the activity of controls and that of 10'5M Pb-treated cells for 4 experiments was only 5% of the average control ATPase activity. When ATPase assays were performed at a range of ATP concentrations with cells treated with 10⁻⁶M and 10⁻⁵M Pb, double reciprocal analysis showed that the kinetics of the ATPase activity appeared altered by the Pb treatment: the Km and for the enzyme were decreased in the Pb treated cells. Measured values were: Controls - Kₘ= 0.13mM, vₘₐₓ- 2.85 μmol Pi/mg protein/hr; 1 μmol Pb - Kₘ= 0.10mM, Vₘₐₓ= 2.62; 10μM Pb - 0.08mM, Vₘₐₓ=2.42 Thus, the measured effect of Pb treatment in culture on measured ATPase activity appears mixed and dependent on ATP concentration: the ATPase activity is inhibited at ATP concentrations above 0.2mM, but stimulated at ATP levels below that. A future, more thorough investigation of this mixed inhibition is warranted. | en |
