Synthesis of urea after a protein-rich meal in normal man in relation to ageing.
An age-related decline in the functional capacity of the liver has been repeatedly demonstrated by means of dynamic tests. We measured the urea-N synthesis rate in response to a protein-rich meal in 24 healthy subjects divided into three age-groups (less than or equal to 55 years, 56-70 years; greater than or equal to 71 years). No differences were observed in the basal state. The peak urea synthesis and the mean urea synthesis in the 5 hours after the meal were blunted with increasing age, and a negative correlation was present between mean or peak urea synthesis and age (r = -0.572 and r = -0.541, respectively). No differences in basal and post-meal total alpha-amino-nitrogen or individual plasma amino acids were observed. Hormone responses were similar. Galactose elimination capacity was also reduced with increasing age, and correlated with mean and peak urea synthesis after a protein mean (r = 0.640 and r = 0.591, respectively). These data suggest that the capacity of the liver to produce urea in response to a protein-rich meal is reduced in the elderly in relation to a decreased functional liver cell mass.
Marchesini
G
G
Istituto di Clinica Medica Generale e Terapia Medica, Università di Bologna, Italy.
Bianchi
G P
GP
Fabbri
A
A
Lolli
R
R
Bugianesi
E
E
Zoli
M
M
Pisi
E
E
D000367:Age Factors; D000368:Aged; D000375:Aging / Q000378:metabolism*; D002986:Clinical Trials as Topic; D004044:Dietary Proteins / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008875:Middle Aged; D013997:Time Factors; D014508:Urea / Q000378:metabolism*
D004044:Dietary Proteins; D014508:Urea