INHIBITORY EFFECT OF ETHANOL ON THE NA-ATPASE ACTIVITY OF RAT-KIDNEY PROXIMAL TUBULAR CELL PLASMA-MEMBRANES()

The inhibitory effect of 2% ethanol (400 mM) in the incubation medium on several characteristics of the Na+-ATPase of basolateral plasma mem branes from rat kidney proximal tubular cells was investigated. Ethano l did not change the K-m, of the enzyme for Mg2+, ATP or Na+; it did n ot change either the optimal pH or temperature values of the incubatio n medium for the enzyme to act and finally, it did not affect the appa rent energy of activation of the enzyme. It was also found that 2% eth anol produced stronger inhibition of the ATPase when it is in an activ ated or stimulated state, than when it is working at its lower basal l evel. The presented results can be explained by assuming that 2% ethan ol in the incubation medium inhibits Na+-ATPase activity by affecting the enzyme structure as well as its activating mechanism.