ABSTRACT
PURPOSE: Atrial natriuretic peptide(ANP) is a hormone with diuretic and natriuretic properties that is released by the atrial stretch and plays an important role in sodium and volume homeostasis. We studied plasma ANP concentration and the influence of ANP on sodium balance after birth in low birth weight neonates on the basis of 34 wks gestational age when the nephrogenesis was completed. METHODS: Twenty low birth weight neonates without congenital heart disease, respiratory insufficiency, renal disease or sepsis born between June 1997 and December 1997 at Korea University Guro Hospital were enrolled in this study. Blood sampling for ANP was done at 6 hr, 12 hr, 24 hr, 3 days, 4 days and 10 days after birth. FENa was calculated by blood and urine electrolyte and creatinine. We analyzed the correlation of plasma ANP concentration and fractional Na excretion rate(FENa). RESULTS: Plasma ANP concentration of low birth weight neonates less than 34 wks was 63.67+/-12.94pg/ml at 6 hr after birth and peaked at 24 hr(110.67+/-6.34pg/ml). Thereafter, it gradually decreased and reached 42.43+/-21.89pg/ml at 10 days(P<0.05). Plasma ANP concentration of low birth weight neonates more than 34 wks was 25.50+/-8.22pg/ml at 6 hr after birth and peaked at 12hours(152.67+/-39.93pg/ml). Thereafter, it gradually decreased and reached 42.78+/-17.67pg/ml at 10 days(P<0.001). And plasma ANP concentration did not correlate significantly with FENa in low birth weight neonates less than 34 wks(r=0.02, P=0.09), but there was good correlation between plasma ANP and FENa in low birth weight neonates more than 34 wks(r=0.6, P<0.001). CONCLUSION: From the above results, it is concluded that ANP influences renal Na excretion after 34-week gestational age when the development of distal tubule, containing ANP receptors, is rapid and contributes to body fluid and Na homeostasis.