URINARY-EXCRETION OF ENDOGENOUS OUABAIN-LIKE SUBSTANCE IN FUROSEMIDE-TREATED NEONATES - ITS RELATION TO RENAL EXCRETORY PATTERN AND ENDOCRINE FACTORS

The present study was undertaken to define the possible role of endoge nous ouabain-like substance (EOLS) in controlling renal excretory patt ern, in mediating the renal responses to furosemide and in inducing en docrine reactions in furosemide-treated neonates. Ten newborn infants with mean birthweight of 2,752 g and mean gestational age of 37.1 week s were given furosemide in a dose of 1 mg/kg. Prior to and following f urosemide therapy, urine was collected for a period of 12 h and analyz ed for creatinine, osmolality, sodium and potassium, as well as for EO LS, arginine vasopressin (AVP), aldosterone and endothelin-1 (ET-1). I n response to furosemide administration, urine flow rate and urinary o smolar, sodium and potassium excretion increased significantly, wherea s creatinine excretion remained unchanged. Furthermore, following furo semide therapy, urinary excretion of EOLS (148.7 +/- 70.8 vs. 200.1 +/ - 98.1 pg/kg/h) and AVP (19.5 +/- 5.4 vs. 27.8 +/- 7.8 pg/kg/h) tended to increase, whereas ET-1 (36.0 +/- 5.6 vs. 61.4 +/- 8.7 fmol/kg/h, p < 0.01) and aldosterone (507 +/- 120 vs. 751 +/- 203 ng/kg/h, p < 0.0 5) increased significantly. Prior to furosemide, urinary EOLS excretio n was found to correlate positively with diuresis (r = 0.80, p < 0.01) , sodium (r = 0.91, p < 0.001), creatinine (r = 0.75, p < 0.001), osmo lar (r = 0.96, p < 0.001), ET-1 (r = 0.90, p < 0.001) and AVP (r = 0.9 2, p < 0.001) excretion. After furosemide, urinary EOLS excretion sign ificantly correlated only with diuresis (r = 0.69, p < 0.05), ET-1 (r = 0.77, p < 0.01) and AVP (r = 0.92, p < 0.001). Urinary EOLS proved t o be independent of aldosterone excretion irrespective of furosemide a dministration. It is concluded that urinary EOLS excretion is closely related to neonatal renal excretory pattern and it may have a role in controlling diuresis and natriuresis. The renal response to furosemide appears to be independent of EOLS, although interdependent endocrine reactions can be induced by furosemide which may modulate the producti on rate and urinary excretion of EOLS.