The effects of different dietary contents of protein on amino acid and glucose production and on the contribution of amino acids to gluconeogenesis in sheep

Abstract

1. Free amino acid entry rates, rates of portal uptake of amino acids and rates of glucose synthesis from amino acids have been measured during the continuous intravenous infusion of [U- 14 C]-labelled mixed amino acids in six sheep receiving diets that supplied different amounts of protein. 2. In four of these sheep and in one other, total rates of glucose production have been measured using continuous intravenous infusions of [U- 14 C]-labelled glucose. 3. A signiiicant correlation was found between total amino acid entry rate ( Y mg/min.kg) and daily protein intake ( X g/kg): Y = 2·14+ 1·38X (r = 0·878, 0·02 > P > 0·01). 4. A significant correlation was found between the rate of absorption of amino acids into the portal system ( Y mg/min.kg) and the daily protein intake ( X g/kg): Y = 0·58 + 0·58X (r = 0·884, 0·02 > P > 0·01). 5. A highly significant correlation was found between total glucose production rates ( Y mglmin. kg) and daily protein intake ( X g/kg): and daily protein intake ( X g/kg): Y = 2.14+ 1.38X (r = 0·878, 0·02 > P > 0·01). Y = 0·375f0·702X (r = 0·866, 0·005 > P > 0·001). 6. The mean proportional contribution to total amino acid entry made by portal absorption was 33·5 f 1·8 yo (six animals). 7. A significant correlation was found between the rate of glucose production from amino acids ( Y mg/min.kg) and the rate of entry of amino acids ( X mg/min.kg): Y = 0-189X-0·414 ( r = 0·84, 0·01 > P > 0·005). 8. The best approximation of the proportion of glucose derived from amino acids was 28·16 f 5·1 % (six animals). 9. The specific radioactivities of amino acids in liver, kidney and muscle did not approach those found in plasma during infusions of [U- 14 C]-labelled mixed amino acids of up to 6·75 h.