AJP - Endocrinology and Metabolism, Vol 238, Issue 1 32-E37, Copyright © 1980 by American Physiological Society
Nitrogen handling in adult hypothalamic obese rats
C. Karakash, F. Rohner-Jeanrenaud, B. E. Hustvedt and B. Jeanrenaud
Several aspects of nitrogen metabolism have been studied in adult
nonhyperphagic, hyperinsulinemic, ventromedial hypothalamus (VMH)-lesioned
rats. Ten days postoperatively, VMH-lesioned rats had high plasma levels of
urea and low plasma tyrosine, while plasma alanine, glutamine, total amino
acid, and protein levels were unaltered. Urea production and excretion were
increased in VMH-lesioned rats. Increased urea synthesis could not be
attributed to enhanced peripheral release of amino acids. In vitro,
measurements of hepatic amino acid uptake and liver protein synthesis did
not reveal any disturbances of these processes in VMH-lesioned rats.
However, hepatic transamination and lipogenesis from amino acids were
increased following VMH-lesions. In addition to the hyperinsulinemia
previously reported to occur in nonhyperphagic VMH-lesioned rats, this
study showed an increased glucagon secretion from perfused pancreases of
these animals. These data together suggest that the excess of the two
hormones at the portal vein of VMH-lesioned rats would favor uptake and
deamination of amino acids, their diversion to lipid synthesis and possibly
other pathways, with consequent increase in urea production and reduced
supply of amino acids to peripheral tissues available for nitrogen
retention.
