Effect of glucagon on plasma alanine and glutamine metabolism and hepatic gluconeogenesis in sheep
Brockman, R.P.; Bergman, E.N.
American Journal of Physiology 228(6): 1628-1633
1975
ISSN/ISBN: 0002-9513 PMID: 1155595 Document Number: 89600
Mature ewes of bodyweight 50 to 60 kg were separately housed and fed every hour during the 24-h test period. One group of 5 sheep served as normal controls and another group of 4 sheep were treated with alloxan, 50 mg/kg with insulin given subcutaneously to maintain normal blood glucose values of about 45 mg/100 ml. The effects of infusion by vein of glucagon were studied in both groups, in conjunction with 3H-labelled glucose for measurement of glucose turnover rates. A continuous infusion of p-aminohippuric acid into a mesenteric vein was used for measurement of hepatic and portal venous plasma flow rates. In experiments with the alloxan-treated sheep, 14C-labelled alanine was infused simultaneously with glucose-6-3H for measurement of plasma alanine turnover, its uptake by the liver and conversion to glucose. The results showed that during glucagon infusion the amount of alanine converted to glucose was significantly increased; a net hepatic extraction of alanine and glutamine and an hepatic output of glutamate both before and during glucagon infusion occurred in both groups of sheep; in addition, during glucagon infusion the hepatic extraction doubled. In general the response to glucagon was sufficiently similar to indicate that the alloxan-treated group can be regarded as a suitable model for the study of glucose synthesis from amino acids.