We describe here an easy method of determining prolidase (EC 3.4.13.9) in plasma after preincubation with Mn2+ for 24 h at 37 degrees C to maximize prolidase activity. The mean activity in 338 patients who were either in hospital or outpatients was 900 U/L +/- 520 (2 SD), unrelated to sex or age. In 25 of these 338 samples tested, prolidase activity was between 1500 and 2000 U/L. It exceeded 2000 U/L in eight, all of whom were patients with chronic liver disease. Plasma prolidase activity was normal in cytolytic syndromes such as liver or heart disease. Of the 27 patients with cirrhosis, only five exhibited prolidase activity greater than 2000 U/L. Plasma prolidase activity was uncorrelated with six biochemical indexes to liver function (the aminotransferases, alkaline phosphatase, glutamyltransferase, total bilirubin, and serum albumin) or with the degree of cirrhotic fibrosis. We believe that plasma prolidase activity may be high only in the early stage of fibrosis. This hypothesis would be consistent with the data on rat-liver collagenolytic activities during CCl4 administration. Monitoring of plasma prolidase activity might be useful in evaluating fibrotic processes in chronic liver disease in the human.
Biotin deficiency was induced in germ-free rats using three experimental protocols. The results showed the important role of biotin during gestation and suckling. The earlier the deprivation, the earlier the deficiency and the severer the symptoms. In this vitamin deficiency, symptoms occurred that were not observed in the control rats, such as the formation of an intestinal volvulus in rats ingesting an L-isoleucine-supplemented diet. The main biochemical anomalies characteristic of propionic acidemia (ketoacidosis and increased urinary elimination of propionic acid) due to propionyl CoA carboxylase deficiency in man were not observed in the rats that were deprived of biotin for 200 days even after a dietary load of L-isoleucine. Only a small urinary excretion of propionyl-glycine and tiglylglycine was observed. We observed a drop in enzymatic propionyl CoA carboxylase activity in the liver that was proportional to the severity of the vitamin deficiency.
Fibroblasts from three galactosaemics had no galactose-1-phosphate uridyltransferase (GALT) activity. These fibroblasts cells were cultured in different media supplemented with dialysed fetal calf serum. Galactosaemic and control cell strains stopped growing in hexose-free medium. In glucose-free medium containing galactose, galatosaemic cells, in contrast to control cells, stopped growing after two days and died. In the same medium supplemented with inosine, they exhibited the same growth pattern as the control cell strains although in the presence of high concentrations of galactose-1-phosphate (Gal-1-P). These findings indicated that the glucose-free medium containing galactose supplemented with dialysed fetal calf serum and inosine, as a ribose donor, was appropriate for further in vitro investigations of galactose metabolism in galactosaemic cells.
In order to obtain an experimental model for studying inherited disorders of galactose metabolism in man, we administered to adult rats a diet supplemented with 50% of galactose during 38 days. The results showed clinical symptoms such as polyuria, polydipsia, growth retardation and bilateral cataract. The main biochemical features were an increase in the galactokinase and uridyltransferase activities in liver, an ubiquitous accumulation in tissues and a considerable urinary elimination of galactose and galactitol, a weak accumulation of galactose-1-phosphate in tissue and a hyperaminoaciduria. This work led us to quantify the respective importance of the major pathway and minor pathways of galactose in the rat after a galactose-rich diet.
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