Chloral hydrate inhibition in vitro of ATPase in membrane of rat erythrocytes and in microsomes of dog kidney external medulla

Abstract

The study of the general anesthetic chloral hydrate and its effects on rat erythrocyte membranes and dog kidney microsomes showed that ATPases were reversibly inhibited in every case. The inhibition was cooperative in the cases of (Mg2+ + Na+ + K+)-ATPase, Mg2+-ATPase and (Na+ + K+)-ATPase of rat erythrocyte membrane, while Ca2+-ATPase and (Mg2+ + Ca2+)-ATPase were non-cooperative. The chloral hydrate concentrations necessary to diminish the activity of the enzyme to half of the Vmax (I50) were 6 mM for Ca2+-ATPase from erythrocyte membranes and 82 mM for Mg2+-ATPase from intact external kidney medulla microsomes. When Ca2+-ATPase was studied in the absence of Mg2+ in these microsomes, the affinity for Ca2+ was very low, but the enzyme was sensitive to chloral hydrate.