Bilirubin photoisomerization products in serum and urine from a Crigler-Najjar type I patient treated by phototherapy.

The relative compositions of the photoisomers of bilirubin-1X alpha (4Z, 15Z-bilirubin) in serum and urine of a patient with Crigler-Najjar type I syndrome treated by phototherapy are reported. High-performance liquid chromatography analysis reveals the presence of high serum levels of the configurational bilirubin photoisomer (4Z,15E-bilirubin) before the beginning of phototherapy (between 12 and 16% of the total bilirubin). The configurational photoisomer value increases during phototherapy with blue fluorescent lamps up to a photoequilibrium of about 25%, similar to that obtained in a bilirubin solution in vitro irradiated by the same lamps. This evidence suggests an inefficient serum excretion of the 4Z,15E-bilirubin. Indeed, its average half-life in serum of the Crigler-Najjar patient is found to be about 8 h. No detectable traces of the bilirubin structural isomer, lumirubin, are found in the serum. On the other hand, lumirubin represents the dominant bilirubin isomer excreted in the urine, as both 15Z and 15E configurations. Smaller amounts of 4Z,15E-bilirubin, 4E,15Z-bilirubin and native 4Z,15Z-bilirubin are observed in urine. The presence in urine of 4Z,15Z-bilirubin is probably due to a fast reversion of the configurational photoisomers to their native form. The half-life of the configurational photoisomers in urine kept at 38 degrees C is found to be of the order of a few minutes. Our study indicates that in Crigler-Najjar type I patients, mechanisms exist to excrete all bilirubin photoisomers. The lumirubin pathway seems to contribute markedly to bilirubin excretion in the urine, as occurs in jaundiced babies under phototherapy. However, the contribution of configurational isomers cannot be neglected.

[Zinc in natural and artificial milk]. / Lo zinco nei latti naturali e artificial

Differences have been observed in both quantitative and qualitative zinc content in human as well as cow milk and colostrum compared to the milk powder preparations which are commonly used as baby's food. It is noteworth that in unprocessed milk and colostrum zinc was present mainly as casein-dependent element, whereas the remaining part of it consisted of immunoglobulin fraction, and only traces were found in the free state. In milk powders zinc showed concentrations lower than in the natural food, and was present mainly as free or protein-independent element. The immunoglobulin fraction of zinc was practically absent from these preparations, while it was found to be a specific component of the natural food (that is, colostrum and milk from all the species examined in the present study).