Volume 6, Number 2, p.p. 57-61
The influence of noradrenaline on the Na,K-ATPase system electrogenicity
L. Shioshvili, T. Jariashvili and Z. Kometiani
I. Beritashvili Institute of Physiology, 14 Gotua Street, 0160 Tbilisi, Georgia
The influence of noradrenaline (NA) on the Na,K-ATPase in the OPM and OPS régimes in the synaptic membranes of a rat’s brain has been investigated. During Na,K-ATPase activation with K+, with the application of NA, it was found that the number of the K+ sites (n) intended for the essential activators in the OPS régime (i.e. the stoichiometry of K+ transport) changes and instead of two becomes one. In the OPM régime, NA does not change the number of essential activators for K+ and remains equal to one. The impact of NA on the mechanism of Na+-activation of Na,K-ATPase in the OPS régime results in the number of the essential activators for Na+ approaching the number of essential activators of Na+ in the OPM régime, i.e. n = 3. The ratio of Na : K stoichiometry changes from 3 : 2 to 3 : 1 and so the electrogenicity coefficient is changed. On the basis of these data, we suggest that NA represents a modifier, which brings the Na,K-ATPase from the OPS régime into the OPM régime. In both régimes the action of NA changes the kinetic parameters.
Keywords: Na,K-ATPase, neurotransmitter, noradrenaline, regulation, stoichiometry