Glucagon influence on gluconeogenesis and oxidation of propionic acid and threonine by perfused ovine liver.

An in situ ovine liver perfusion technique was developed and used to study glucagon effects on utilization of simultaneously infused propionic acid and amino acids. Physiological amounts of propionic acid and amino acids (hydrolyzed casein) were infused into livers along with carbon-14 propionic acid or carbon-14 threonine with and without glucagon. Glucagon (5 mg) caused a 75% increase of glucose synthesis and a 19% increase of labeled carbon dioxide production from carbon-14 propionic acid. There also was a decrease of perfusate urea nitrogen when glucagon was present. Glucagon caused a 76% decrease of carbon-14 threonine utilization by ovine livers, and labeled carbon dioxide production from carbon-14 threonine was only 38% of control when glucagon was infused. From these results, glucagon caused an increase of use of propionic acid and a decrease of use of threonine for energetic pathways in sheep liver. Therefore, glucagon directly or indirectly may mediate amino acid sparing by ruminant liver.