NA, K-ATPASE AND CL-ATPASE REGULATION BY DOPAMINE.

The influence of dopamine (DA) on the Cl-ATPase and Na, K-ATPase in the synaptic membrane fraction of the rat brain has been investigated. The fraction was obtained by differential centrifugation. To analyze the function of Na, K-ATPase, and Cl-ATPase, we have applied the method of kinetic analysis of multi-sited enzyme systems, which has been described as the only method used for kinetic investigation of multi-sited enzyme systems. Dopamine does not alter the stoichiometry of Cl- transport. The number of the Cl- sites intended for the essential activator (n) remains 1. During Na, K-ATPase activation with K+, with the application of DA, it was found that the number of the K+ sites intended for the essential activators (i.e. the stoichiometry of K+ transport) changes, and instead of two becomes one. The impact of DA on the mechanism of Na+-activation of Na, K-ATPase results in the unchanged number of essential activators for Na+ (n=3). The ratio of Na: K stoichiometry changes from 3:2 to 3:1 and so the electrogenicity coefficient is changed.