The excretion of sulfur compounds in the urine of newborn infants.

The excretion of sulfur-containing compounds was determined on the third and sixth day of life in male infants and the results were compared with those previously obtained on fed and fasting men. The output of total sulfur and inorganic sulfate was very low on the third day of life but had increased by the sixth day to levels found in the fasting men, whereas the excretion of mercaptolactate in the newborns decreased from the third to the sixth day of life. These results may be explained by the initial fasting state of neonates followed by an anabolic phase. Neonates excreted acid-labile ester sulfate and mercaptoacetate at levels similar to those found in adults, but the neonatal urine also contained sulfate esters (probably steroid sulfates) that required more drastic acid conditions for hydrolysis. Raised concentrations of sulfur-containing amino acids (methionine, cystathionine, cyst(e)ine and taurine) were found in neonatal urine in confirmation of earlier reports. The excretion of thiosulfate could only be determined in newborns on the sixth day and was low in comparison with that of adults. High urinary thiocyanate concentrations were found in newborns fed by tobacco-smoking mothers, whereas the excretion of thiocyanate was low in other newborns. The possible medical hazards from the exposure of neonates to thiocyanate are emphasized.