Effects of stabilizers in preparations of human serum albumin on the serum bilirubin in Gunn rats.

Abstract

ABSTRACT. Commercially available preparations of human serum albumin (HSA) containing stabilizers (i.e. 16 mmol/I Na caprylate plus 16 mmol/I Na N‐acetyl‐dl‐tryptophan) were injected either s.c., i.p. or i.v. into homozygous infant Gunn rats. 30 min and 3 hours after s.c. injection, a serum bilirubin decline which surpassed dilution by the injected volume could be ascertained. It was mainly caused by N‐acetyl‐dl‐tryptophan since s.c. injections of appropriate amounts of this substance alone or a mixture of both components of the stabilizer without HSA brought about similar results. HSA without these stabilizers had not such an effect. It is postulated that under these conditions Na N‐acetyl‐dl‐tryptophanate displaced bilirubin from albumin bonds. It became obvious that after s.c. injection equilibration of HSA between skin and plasma was delayed, whereas Na N‐acetyl‐dl‐tryptophan was rapidly transported to the blood. As for Na caprylate, a displacing effect of short duration could not be excluded by the experimental arrangement used, since the metabolism of the substance in the rat is very fast. When HSA and the stabilizers entered the plasma simultaneously (i.v. injection) no effect on serum bilirubin concentration could be proved 30 min and 3 hours later. All the bilirubin and the Na N‐acetyl‐dl‐tryptophan present in the plasma at that time can be bound to the large amount of albumin which is directly given into the circulation of the animal. 30 min after i.p. injection of HSA preparations containing stabilizers a small decrease of serum bilirubin concentration could be recognized. It was less pronounced and less persisting than after s.c. injection. Probably equilibration of HSA between peritoneum and plasma went on faster than between skin and plasma. Only for a short period a lack of albumin binding sites in the plasma of the rat pointed to a surplus of Na N‐acetyl‐dl‐tryptophan.