Nitrogen metabolism during liver regeneration.

Nitrogen metabolism was investigated in regenerating liver-bearing rats through the following parameters: (1) liver aminoacid content, (2) plasma and urinary urea and creatinine, (3) plasma and urinary oxypurines, uric acid and allantoin. Two groups of aminoacids were considered: (1) the essential aminoacids (phenylalanine, tyrosine, isoleucine, lysine, leucine, valine, arginine, histidine and methionine); (2) the non-essential aminoacids (aspartic acid, asparagine, glutamic acid, glutamine, alanine, glycine, serine, threonine and proline). Some of the first group tended to decrease, and those of the second group to increase, immediately after partial hepatectomy. Few ketogenic aminoacids are probably oxidized to provide energy. The flux of aminoacids for gluconeogenesis is minutely controlled, therefore, those of the second group being spared at first and set aside for protein synthesis, which increases on the second and third days after partial hepatectomy. Plasma and urinary urea, oxypurines, uric acid and allantoin did not show any significant variations after partial hepatectomy. The conclusion emerging from the present research is that, although variations in aminoacid composition and metabolism and in purine nucleotide metabolism have been demonstrated to occur in the regenerating liver, the overall nitrogen catabolism, as reflected by the principal end products, does not undergo substantial variations. The remaining liver is able to fulfil this function.