A method for the isolation of the amide nitrogen of glutamine from biological samples for mass spectrometry

The amide nitrogen from L-glutamine has been isolated from an artificial plasma, in a form suitable for mass spectrometry, by a macromodification of the glutaminase reaction. The prior removal of free ammonia was carried out by alkaline aeration. When this was performed at 0§C for 3 h, spontaneous hydrolysis of glutamine was 1.4 percent. Cross-contamination with nitrogen liberated from the amide group of asparagine can be avoided by preincubation with asparaginase for 2h and removal of the freed ammonia prior to reacting with glutaminase. Hydrolysis of glutamine during this step is 12 percent. Measurements of enrichment can be made on samples yielding more than 1 æmol of glutamine amide-derived ammonia.(AU)

Glutamine production rate and its contribution to urinary ammonia in normal man

Glutamine [15N]amide was infused at a steady rate of 33.34 micromoles/h into seven male adult volunteers who were in the fed state and normal acid-base status. Plasma glutamine amide N enrichment and urinary ammonia N enrichment rose to a constant value within 3h. The glutamine production rate was 51.8 ñ 7.9 millimoles/h. The total ammonia execretion rate was 0.87 millimoles/h. Of this excreted ammonia 62.6 ñ 9 percent was derived from the amide N atom of glutamine. The excreted glutamine amide N (0.53 millimoles/h) was only 1 percent of the glutamine production. If half the ammonia formed by the kidney is excreted in urine and half liberated into the renal vein in subjects with normal acid-base status [E. E. Owen & R. R. Robinson (1963) Journal of Clinical Investigation, 42, 263-276], then the kidney accounts for only 2 percent of glutamine disposal. Whole body protein turnover, measured from the urinary [15N]ammonia enrichment, was 30.3 ñ 7.7 g of N/day (2.8 g of protein/day/kg). (AU)

Hepatic function in rats with dietary-induced fatty liver, as measured by the uptake of indocyanine green

The hepatic uptake of indocyanine green (ICG) has been measured in rats receiving a 50 g protein/kg diet for 6, 12 or 20 d or a choline-deficient diet for 2 or 6 d. There was no effect on ICG uptake on the choline-deficient diet, although all the rats developed an intense fatty infiltration of the liver by 6 d. The rats on the 50 g protein/kg diet showed impaired uptake of ICG at 6, 12 and 20 d, which appeared to be related to the extent of fatty infiltration. It is concluded that ICG uptake is predominantly a function of the periportal zone of the liver lobule, and therefore likely to be sensitive to insults that exert their predominant effect in this zone. (AU)

The effects of a protein-deficient and a choline-deficient diet on the liver function of adult rats, as measured by the rate of uptake of indocyanine green

It is shown that in children suffering from protein calorie malnutrition the mortality associated with fatty liver and liver failure is high. This study was designed to measure functional liver capacity using kinetics analysis of ICG uptake by the liver in animal models of malnutrition and fatty liver disease. Two models were used. Rats were kept either on a 5 percent low protein diet for 6, 12 and 20 days, or on a choline deficient diet for 2 and 6 days. Fatty liver developed in both groups of animals although the changes on the choline deficient diet were more marked than on the protein deficient diet. The choline deficient animals developed a more intense fatty liver at an earlier stage. On the low protein diet the accumulation of fat was inversely correlated to the change in the rate of hepatic uptake of ICG. This relationship could not be demonstrated in the choline deficient group; however, these animals did show a negative correlation between the rate of ICG uptake and FFDLW. It is suggested that the rate of ICG uptake may reflect the rate of liver is discussed in this light (Summary)