Antenatal corticosteroid therapy for the prevention of respiratory distress syndrome has been shown to have a wide range of extrapulmonary effects. This treatment has been demonstrated to influence water and electrolyte homeostasis by accelerating renal functional maturation and increasing skin hydrophobicity. Na+-K+-ATPase is a ubiquitious plasma membrane-bound class of enzymes responsible for Na+ and K+ translocation across cell membranes. The activity of this enzyme increases after antenatal corticosteroid treatment in the kidney of late gestation fetal sheep. In the brain, Na+-K+-ATPase maintains electrochemical gradients and cell volume. Therefore, we examined the effects of maternal antenatal corticosteroid administration upon Na+-K+-ATPase activity in the cerebral and renal cortex of fetal sheep at 80% or 120 days of gestation. Intramuscular injections of either dexamethasone or placebo were given to the pregnant ewes as four 6 mg doses every 12 hr starting 48 hr before harvest of cerebral and renal cortex. Na+-K+-ATPase activity was estimated in crude total membrane preparations by the measurement of ouabain sensitive inorganic phosphate liberation from ATP expressed as mmoles Pi/mg protein/hr. In the cerebrum, Na+-K+-ATPase activity in the fetuses of placebo and dexamethasone pretreated ewes was 12.56± 2.80 (n=6, M ± SD), and 12.04 ± 1.86 (n=7, p=0.55), respectively. Dexamethasone pretreatment increased renal activity from 6.42± 1.23 to 8.65 ± 0.78 (n=4, p<0.02). Therefore, antenatal administration of dexamethasone to pregnant ewes in clinically relevant doses did not change the activity of Na+-K+-ATPase in the cerebrum of fetuses at 80% of gestation. In contrast, in the kidneys of these fetuses, antenatal dexamethasone treatment increased Na+-K+-ATPase activity. We conclude that antenatal steriods appear to differentially regulate regional Na+-K+-ATPase activity in brain and kidney of fetal sheep at 80% of gestation.
Supported by NIH HD34618
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Petersson, K., McDonough, A., Padbury, J. et al. Antenatal Steroid Treatment Differentially Affects Cerebral and Renal Cortical Na+-K+-ATPase Activity in Ovine Fetuses ♦ 347. Pediatr Res 43, 62 (1998) doi:10.1203/00006450-199804001-00368