Effect of chronic ethanol treatment on specific [3H]ouabain binding to (Na+ + K+)-ATPase in different areas of cat brain

Sharma, Virendra K.; Banerjee, Sipra

doi:10.1016/0014-2999(79)90259-0

Cited by 6 publications

(1 citation statement)

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“…The suggestion has been made that kinetic alterations are secondary to increased intracellular sodium concentrations and are best explained by increased numbers of Na+,K+-ATPase pumps in the membrane (1,6,7). The question of whether increases in Na+,K+-ATPase activity are the result of altered kinetic properties of the enzyme or increased numbers of pumps has remained open except for one report of anatomically discrete increases in ouabain binding to brain tissue from cats (16).…”

Section: Discussionmentioning

confidence: 99%

Increases in Na+,K+-ATPase activity of erythrocytes and skeletal muscle after chronic ethanol consumption: evidence for reduced efficiency of the enzyme.

Johnson¹,

Crider²

1989

Proc. Natl. Acad. Sci. U.S.A.

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Increased Na',K+-ATPase activity observed after chronic ethanol consumption has been examined to determine whether the increase is due to changes in the kinetic properties of the enzyme or increases in the amount of enzyme in the membranes examined. In skeletal muscle and erythrocyte ghosts from rat, as well as from humans, increased Na',K+-ATPase activity in ethanol-consuming individuals was not accompanied by an increase in the number of ouabain binding sites. In studies with intact human erythrocytes, similar ouabain-sensitive 22Na' and 8'Rb+ pumping rates were observed between normal and ethanol-consuming individuals and the Na' to Rb+ pumping ratio was found to be 1.5 in all cases. However, ouabain-sensitive lactate plus Pi formation was increased in cells from alcoholic individuals. Thus these data suggest that increased enzyme activity may be due to a kinetic alteration of the Na',K+-ATPase and that the enzyme may be less efficient in coupling ion pumping to ATP hydrolysis than the enzyme in normal cells.Experimental models examining the effects of alcoholism on cation transport have resulted in persistent reports that Na',K+-ATPase activity of skeletal muscle (1), erythrocyte (2, 3), brain (2, 4), and liver (5) plasma membranes is increased. This increase has been postulated to be a secondary consequence of decreased membrane resistance and increased membrane sodium permeability that result in a rise in intracellular sodium concentrations (1, 6, 7). Because these measurements have been made under conditions assessing Vmax of the Na+,K+-ATPase, the simplest explanation for increased activity is an increase in the number Na+,K+-ATPase pumps in the plasma membrane (1-7).In testing this hypothesis, we have measured Na+,K+-ATPase activity and ouabain binding in rat skeletal muscle and in intact erythrocyte and ghost preparations from rats and humans after chronic ethanol consumption. Although all criteria used for evaluating ATP hydrolysis rates indicate increases in Na+,K+-ATPase activity, which is quantitatively similar to previous findings (1-3) from alcoholic individuals, the ion pumping rates, the ion pumping ratios, and the number of ouabain binding sites were not different from controls. These data suggest a kinetic alteration of the enzyme consistent with less efficient coupling of ATP hydrolysis to ion pumping. MATERIALS AND METHODSMale Sprague-Dawley rats weighing 200-300 g (Sasco, Omaha, NE) were fed 7% (vol/vol) ethanol ad libitum as a liquid part of their diet for 28 days. Age-matched control animals of equivalent size were fed the same diet supplemented with Polycose (Ross Laboratories, Columbus, OH) to approximate caloric differences in the two test groups. Animals were anesthetized by injection with 100 mg of inactin per kg (body weight) and 10 ml of blood was collected in syringes containing 1 ml of acid citrate/dextrose as an anticoagulant. Hind-limb skeletal muscle [5 g (wet weight)] was collected and visible fat and connective tissue were removed by sharp dissection. We have descri...

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Section: Discussionmentioning

confidence: 99%