POSTASPHYXIAL REOXYGENATION REDUCES THE ACTIVITY OF NA+ K+-ATPASE IN THE ERYTHROCYTES OF NEWBORN PIGLETS/

The aim of our study was to determine whether the impairment of Na+/K pump is detectable in erythrocytes during hypoxia and reoxygenation. Acute asphyxia was induced in 10 newborn piglets for Ih by bilateral p neumothorax. The Na+/K+-ATPase activity, Na+, K+ and ATP content of RB Cs were determined in baseline condition (p(a)O(2): 60.4 +/- 9.3 mm Hg ), at the end of the hypoxic period (1 h) (p(a)O(2): 30.2 +/- 10.3 mm Hg), then hourly during the reoxygenation phase (2, 3, 4 h) (p(a)O(2): 54.8 +/- 9.0, 56.1 +/- 8.7, 57.2 +/- 9.6 mm Hg). The Na+/K+-ATPase ac tivity was constant during the first 3 h. However, it decreased at 4 h (676 +/- 168 versus baseline 833 +/- 141 U, p < 0.05). The highest AT P content was measured also at this point (4.32 +/- 0.57 versus baseli ne 3.27 +/- 0.45 mmol/l RBC, p < 0.01). The Na+ content was lower at 1 and 2 h (14.0 +/- 1.8; 13.8 +/- 1.2 versus baseline 15.7 +/- 1.2 mmol /100 g Hb, p < 0.05), but later it became normal. Plasma monovalent ca tionic levels and intracellular K+ content did not alter during the ex periment. Our results indicate that the deterioration of enzyme activi ty occurs within the same time-frame that previously described morphol ogical alterations in brain tissue develop, so the RBC Na+/K+-ATPase a ctivity might reflect the progress of posthypoxial brain damage.