Bilirubin-like material in urine of normal adults

Abstract

1. 1. At pH 3.5 unconjugated and conjugated bilirubin are quantitatively adsorbed on talcum. Adsorbed bile pigments were quantitated by reaction with either the diazonium salt of sulphanilic acid or with the diazonium salt of ethyl anthranilate, followed by conversion of the azopigments to the zinc(II) complexes. Adsorption of urinary bile pigments is maximal at pH 3.5 as compared to higher pH values. 2. 2. Of urinary bilirubin equivalents (normal concentration: 1.3mg/l) only 12.5% are adsorbed on talcum, at pH 3.5. It is demonstrated that bile pigments of the types known up to date can be expected to be adsorbed quantitatively under these conditions. The adsorbable urinary bile pigments could not be extracted from urine with chloroform and reacted completely with the diazonium salt of ethyl anthranilate ( i.e., in the absence of an accelerator). These observations provide strong evidence against the presence of unconjugated bilirubin in normal urine. Of the azopigments derived from the adsorbed material 88% corresponded chromatographically to authentic azobilirubin. 3. 3. The nature of bile pigments present in normal urine is discussed.