The prognostic value of the brain sodium-potassium ATPase enzyme concentration in head injury

The importance of systemic response in the pathobiology of blast-induced neurotrauma

Due to complex injurious environment where multiple blast effects interact with the body parallel, blast-induced neurotrauma is a unique clinical entity induced by systemic, local, and cerebral responses. Activation of autonomous nervous system; sudden pressure increase in vital organs such as lungs and liver; and activation of neuroendocrine-immune system are among the most important mechanisms that contribute significantly to molecular changes and cascading injury mechanisms in the brain. It has been hypothesized that vagally mediated cerebral effects play a vital role in the early response to blast: this assumption has been supported by experiments where bilateral vagotomy mitigated bradycardia, hypotension, and apnea, and also prevented excessive metabolic alterations in the brain of animals exposed to blast. Clinical experience suggests specific blast-body-nervous system interactions such as (1) direct interaction with the head either through direct passage of the blast wave through the skull or by causing acceleration and/or rotation of the head; and (2) via hydraulic interaction, when the blast overpressure compresses the abdomen and chest, and transfers its kinetic energy to the body's fluid phase, initiating oscillating waves that traverse the body and reach the brain. Accumulating evidence suggests that inflammation plays important role in the pathogenesis of long-term neurological deficits due to blast. These include memory decline, motor function and balance impairments, and behavioral alterations, among others. Experiments using rigid body- or head protection in animals subjected to blast showed that head protection failed to prevent inflammation in the brain or reduce neurological deficits, whereas body protection was successful in alleviating the blast-induced functional and morphological impairments in the brain.

Effect of gamma-hydroxybutyric acid on tissue Na+,K- ATPase levels after experimental head trauma

BACKGROUND

A failure of the Na(+),K(+)-ATPase activity (which is essential for ion flux across the cell membranes) occurs in many pathological conditions and may lead to cell dysfunction or even cell death. By altering the concentration of specific opioid peptides, gamma-hydroxybutyric acid (GHB) may change ion flux across cell membranes and produce the 'channel arrest' which we assumed will inhibit the failure of Na+,K(+)-ATPase activity and therefore lead to energy conservation and cell protection. Therefore we planned this study to see the effects of GHB at two different doses on Na(+),K(+)-ATPase activity in an experimental head trauma model.

METHODS

Forty New Zealand rabbits were divided equally into four groups: group I was the sham-operated group, group II (untreated group), group III received head trauma and intravenous (i.v.) 500 mg/kg GHB and group IV received head trauma and i.v. 50 mg/kg GHB. Head trauma was delivered by performing a craniectomy over the right hemisphere and dropping a weight of 10 g from a height of 80 cm. The non-traumatized (left) side was named as 'a' and the traumatized (right) side as 'b'. One hour after the trauma in groups II and III and craniotomy in group I, brain cortices were resected from both sides and in group I only from the right side was the tissue Na-K-ATPase activity determined.

RESULTS

The mean +/- SD of Na(+),K(+)-ATPase levels of each group are as follows: group I - 5.97 +/- 0.55; group IIa - 3.90 +/- 1.08; group IIb - 3.58 +/- 0.90; group IIIa - 5.53 +/- 0.60; group IIIb - 5.33 +/- 0.88; group IVa - 5.05 +/- 0.72; group IVb - 4.93 +/- 0.67. The Na(+),K(+)-ATPase levels of group IIa, IIb, IVa and IVb were significantly different from group S (P < 0.05). There were also significant differences between group IIa and groups IIIa and IVa; group IIb and groups IIIb and IVb (P < 0.05).

CONCLUSIONS

We conclude that GHB is effective in suppressing the decrease in Na(+),K(+)-ATPase levels in brain tissue at two different dose schedules after head trauma.

Sex-dependent changes in blood-brain barrier permeability and brain NA(+),K(+) ATPase activity in rats following acute water intoxication

To understand the increased susceptibility of the development of serious complications to hypoosmotic hyponatremia in young females, we examined the resistance of blood brain barrier (BBB) permeability to water along with the synaptosomal Na(+),K(+)ATPase activity in both sexes of rats during acute water intoxication. Four groups of rats were used: Group I and II were normal female and male rats injected with only Evans-blue. Group III and IV were water intoxicated female and male rats respectively. BBB permeability in female rats was found to be increased following acute water intoxication. In contrast, synaptosomal Na(+),K(+)ATPase activities in both water intoxicated male and female rats were found significantly lower than those in control rats. But inhibition in enzyme activity in synaptosomes from water intoxicated female rats was more pronounced than those of corresponding male rats. Our results concluded that female sex steroids may be responsible for the highly significant decrease in synaptosomal Na(+),K(+)ATPase activity and increased BBB permeability in female rats following water intoxication.