Serum digoxin-like immunoreactive factor in children and its relation to sodium metabolism

Abstract

Serum digoxin-like immunoreactive factor (DLIF), an endogenous substance that cross-reacts with antidigoxin antibodies, was assessed (fluorescence polarization immunoassay) in children (n = 134) aged 5-16 y, who had never been treated with cardiac glycosides. DLIF was found in 50% of serum samples at a mean concentration of 0.16 +/- 0.06 ng/ml (range 0.03-0.35 ng/ml). Although the study population as a whole was apparently homogeneous with regard to serum sodium content, and none had clinical signs of sodium imbalance, children with DLIF showed significantly lower natraemia (p = 0.0002), higher urinary concentration (p = 0.001) and fractional excretion (p = 0.001) of sodium, and increased systolic blood pressure (p = 0.009) compared with children without DLIF. Inverse correlations were found between DLIF concentration and serum sodium (p < 0.01), urine sodium content (p < 0.001), 24-h sodium excretion (p < 0.001), systolic (p < 0.001) and diastolic (p < 0.01) blood pressure. These findings suggest that sodium handling is different in children with and without DLIF, since this material seems to be released preferably in subjects who show a trend towards negative sodium balance. Such an association suggests that DLIF may be a physiologically relevant material involved in sodium homeostasis.

Role of Digoxin-Like Immunoreactive Substance in the Pathogenesis of Transient Tachypnea of Newborn

“…DLIS has a natriuretic effect in term and preterm neonates [18, 19, 38]. Our TTN group had higher serum Na + , osmolarity, diuresis, and FeNa + levels, both on the 1st and 7th days, compared to the control group.…”

“…The role of Na + -K + -ATPase in alveolar fluid clearing has been shown in animal models [28–30]. Besides, DLIS has been shown as an inhibitor of Na + -K + -ATPase in in vitro and in vivo studies [15–18, 31, 32]. However, its role in TTN pathophysiology has not been investigated so far.…”

“…In some disorders, such as hypertension, acromegaly, liver diseases, and renal and cardiac failure, high DLIS level was observed in the blood, despite no digoxin use [17]. In newborns, especially in preterm infants, unrelated to the maternal and placental levels, DLIS levels were reported to be much higher than the other pediatric age groups [18–21]. …”