Plasma lipid peroxide levels were studied in 40 children with chronic cholestasis comprising 21 with syndromatic paucity of interlobular bile ducts (PILBD) and 19 with biliary atresia. Compared to the controls, mean lipid peroxide values were twice as high in children with biliary atresia (4.56 +/- 2.28 nmol/ml) and four times as high in those with PILBD (9.62 +/- 3.3 nmol/ml). These differences are highly significant. In patients with biliary atresia, the increase in lipid peroxide levels was clearly related to the bilirubin, cholesterol and phospholipid concentrations. In the PILBD group, however, there was little evidence of such a relationship. Vitamin E treatment seemed to have no effect on these increased lipid peroxide levels during the evolution of chronic cholestasis, and further investigations are necessary to clarify the pathological mechanisms involved.

The transport of L-alanine in human diploid fibroblasts was investigated. Transport measurements were performed on subcultures between the third and eighth passages with subconfluent cells growing on glass coverslips. Kinetic analysis of approximate initial rates of transport at substrate concentrations from 0.05 to 10 mmole/liter indicate the presence of two distinguishable systems. The high affinity system has a Km of 0.24 mmole/liter and a Vmax of 6.4 nmole/100 micrograms protein/2 min. For the low affinity system, the contribution of the high affinity system to the uptake must absolutely be taken into account. The Km and Vmax values, obtained by using a computer program, are a Km of 15.0 mmole/liter and a Vmax of 14.7 nmole/100 micrograms protein/2 min. For alanine concentrations below 1 mmole/liter, the contribution of the Na+-independent uptake is less than 10%, and the kinetic constants of the high affinity system are in the same range if this contribution is taken into account. On the contrary the influence of a diffusion-like process is more significant on the low affinity system whose Km is about 49 mmole/liter after subtraction of the Na+-independent uptake from the experimental velocities. Inhibition studies were performed with NCH3-alanine. They permitted us first to confirm the existence of system A in cultured human fibroblasts in agreement with two recent works and second to show how this system contributes to L-alanine uptake. This contribution seems very small in low concentrations but it rises as the concentrations increase.

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