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Functional and structural properties of Na+/K(+)-ATPase enzyme in neonatal erythrocytes
B Vásárhelyi1, A Vér, A Nobilis
1Semmelweis Medical University, Budapest, Hungary.
Insights
Neonates exhibit higher Na+/K(+)-ATPase enzyme activity and specific subunit expression compared to children. This suggests differences in cell membrane regulation and potential resistance to cardiac glycosides in newborns.
Area of Science:
- Biochemistry
- Pediatrics
- Molecular Biology
Background:
- The Na+/K(+)-pump is crucial for regulating intracellular monovalent cation concentration.
- Limited data exist on Na+/K(+)-pump structure and function in healthy neonates compared to children.
Purpose of the Study:
- To investigate the activity, ouabain sensitivity, and subunit isoform expression of Na+/K(+)-ATPase in healthy neonates and children.
- To compare the molecular characteristics of the Na+/K(+)-pump between these two age groups.
Main Methods:
- Blood samples were collected from 53 healthy neonates and 61 healthy children.
- Na+/K(+)-ATPase activity, ouabain inhibition (I50), and subunit isoform expression were determined.
Main Results:
- Neonates showed significantly higher Na+/K(+)-ATPase activity and I50 values for ouabain inhibition compared to children.
- Higher expression of alpha 1 subunits and a greater alpha 1/alpha 2 ratio were observed in neonates.
Conclusions:
- This study is the first to show changes in Na+/K(+)-ATPase at both enzyme activity and protein levels between neonates and children.
- Findings may explain the reduced sensitivity of neonatal cell membranes to cardiac glycosides.
Background:
The Na+/K(+)-pump is the main regulator enzyme of intracellular monovalent cation concentration. There are only limited data available concerning its structure and function in healthy neonates, in comparison with data available regarding its structure and function in children.
Patients And Methods:
Samples of 100 microL of anticoagulated blood were taken from 53 healthy neonates (age under 6th postnatal day, median age 3.5 days) and 61 healthy children (median age 12.4 months, range 6-36 months,). The Na+/K(+)-ATPase activity, its sensitivity to ouabain (a digoxin-analogue substance) and the expression of Na+/K(+) ATPase subunit isoforms were determined.
Results:
The enzyme activity (429.2 +/- 17.2 versus 295.5 +/- 10.2 U, P < 0 x 0.001) and I50 value for ouabain inhibition (1.50 +/- 0.10 versus 0.96 +/- 0.10 mumol L-1, P < 0.05) was higher in neonates. More alpha 1 subunits (relative density: 1.16 +/- 0.10 versus 0.75 +/- 0.03, P < 0.001) and higher alpha 1/ alpha 2 ratio (4.14 +/- 0.21 versus 2.02 +/- 0.16, P < 0.01) were detected.
Conclusion:
This is the first study demonstrating changes of Na+/K(+) -ATPase molecules not only in enzyme activity, but also on protein level. Our results might contribute to the understanding of the resistance of neonatal cell membranes toward the pharmacodynamic actions of cardiac glycosides.