Acute stress stimulates the red cell sodium pump in rat

The effect of restraint stress (RS) on the red cell sodium pump, hematocrit, plasma osmolality and plasma sodium and potassium concentrations was measured. Ten min of RS did not produce any change in the sodium pump activity. Longer lasting stress - 150 min - stimulated significantly the sodium pump activity in comparison to the control group (8.52 +/- 0.76 vs. 7.78 +/- 0.46 min-1 per 10(13) Ery; P less than 0.05; means +/- S.D.). Hematocrit rose during the stress (controls: 44.8 +/- 2.3; 10 min RS: 48.1 +/- 1.1; 150 RS: 47.0 +/- 1.9%; P less than 0.01 and P less than 0.05, respectively). The values for osmolality and plasma sodium concentration did not change. However, the plasma potassium concentration decreased significantly after 150 min of RS (4.63 +/- +/- 0.74 vs. 3.3 +/- 0.48 mmol 1(-1); P less than 0.001). Thus, acute stress stimulates the sodium pump activity in erythrocytes of the rat and norepinephrine seems most likely to trigger this activation.