title: Protein and amino acid metabolism during early starvation as reflected by excretion of urea and methylhistidines.
abstract: Endogenous excretion of nitrogenous products was studied during early starvation in six healthy, nonobese subjects after six days on a well-defined diet, designed to achieve net protein balance and an adequate calorie supply. The diet contained 0.5 g myofibrillar-free protein and 35 kcal/kg body weight. The subjects then fasted for three days. Urine was collected for 24-hour periods and analyzed for urea, ammonia, 3-methylhistidine, and 1-methylhistidine. Blood glucose and serum urea levels were measured daily. In a second group of subjects, muscle biopsies for determination of free amino acid concentrations were taken in the overnight fasted state and after three days of fasting. During the period with a balanced diet, urea production fell initially and stabilized after two to three days at a level of 146 +/- 15 mmol/24 h. During the period of fasting, serum urea increased from 3.0 +/- 0.4 to a maximum value of 6.2 +/- 0.7 mmol/L and urea production rose markedly, to a peak of 293 +/- 16 mmol/24 h. Ammonia excretion was 24 +/- 2 mmol/24 h before and 71 +/- 13 mmol/24 h after three days of fasting. 3-Methylhistidine excretion was stable before fasting and then rose from 154 +/- 17 to 198 +/- 17 mumol/24 h. 1-Methylhistidine excretion was unchanged during fasting. Blood glucose levels were stable at 4.8 +/- 0.2 mmol/L before fasting and then fell to 3.7 +/- 0.3 mmol/L. Intracellular concentrations of amino acids in skeletal muscle decreased markedly during fasting; after three days of fasting the glutamine concentration had fallen by 34%.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anaesthesiology, Karolinska Hospital, Stockholm, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Giesecke
authors.forename: I
authors.initials: I
authors.lastname: Magnusson
authors.forename: M
authors.initials: M
authors.lastname: Ahlberg
authors.forename: L
authors.initials: L
authors.lastname: Hagenfeldt
authors.forename: J
authors.initials: J
authors.lastname: Wahren
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000378:metabolism*; D000641:Ammonia / Q000652:urine; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D003404:Creatinine / Q000652:urine; D004032:Diet; D005260:Female; D006639:Histidine / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008762:Methylhistidines / Q000378:metabolism* / Q000652:urine; D009132:Muscles / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D013217:Starvation / Q000378:metabolism*; D013997:Time Factors; D014508:Urea / Q000378:metabolism* / Q000652:urine
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D008762:Methylhistidines; D011506:Proteins; D006639:Histidine; D000641:Ammonia; D014508:Urea; D003404:Creatinine