Key result
Repeated immobilization stress increases rat left ventricular Na+/Ca2+ exchanger activity independent of cortisol.
Why the study?
The effect of immobilization stress on the Na+/Ca2+ exchanger expression in rat heart ventricles and atria and the role of cortisol in this process were unclear.
Immobilization stress increases Na+/Ca2+ exchanger expression and activity in the rat left ventricle through a mechanism independent of cortisol.
Suggests stress may asymmetrically alter LV calcium handling; leaves open human relevance and requires validation.
Calcium homeostasis is crucial for the proper function of cardiac cells. Since the Na(+)/Ca(2+) exchanger is an important modulator of calcium homeostasis especially in the heart, the objective of this study was to investigate the effect of immobilization stress on the high capacity Na(+)/Ca(2+) exchanger in rat heart ventricles and atria. Repeated immobilization stress increased both the mRNA and the protein level and the activity of the Na(+)/Ca(2+) exchanger in the left, but not the right ventricle of rat heart. Since corticosterone is rapidly increased during the stress stimulus, it might be assumed that mRNA of the Na(+)/Ca(2+) exchanger is increased through a glucocorticoid responsive element. However, we have found that cortisol did not change the Na(+)/Ca(2+) exchanger at the mRNA or protein levels. These results clearly show that this effect of stress is not mediated via cortisol.
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Záciková et al. (1999) studied this question. Immobilization stress and cortisol was evaluated on mRNA, protein level, and activity of the Na+/Ca2+ exchanger. Repeated immobilization stress increased the mRNA, protein level, and activity of the Na+/Ca2+ exchanger in the left ventricle of rat hearts, an effect that was not mediated by cortisol.
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