Single-column chromatographic analysis of labeled glutamine and other amino acids in whole blood.

A method is presented for single-column analysis of the concentrations and specific activities of the free amino acids in both whole blood and plasma. Interference from glutathione in whole blood was eliminated by the use of sodium sulfite although losses of about one-half of the cystine and methionine occurred. Seventy-five percent +/- 1 of the glutamine was recovered consistently in both whole blood and plasma so that corrections for this loss readily could be made. Elimination of the baseline shift due to ammonia was accomplished by passing the buffers through ion-exchange columns before entering the sample loops. There were several significant differences between amino acid concentrations and specific activities in whole blood and in plasma, indicating that care should be taken in interpreting data on metabolism of amino acids.

Effects of glucagon and insulin on net hepatic metabolism of glucose precursors in sheep.

The net hepatic metabolism of amino glycerol, lactate, and pyruvate was determined in conscious fed sheep by multiplying the venoarterial concentration differences by the hepatic blood or plasma flow. In each experiment several sets of control blood samples were taken; glucagon or insulin then was infused intraportally for 2 h during which additional samples were taken. Four types of experiments were performed: 1) glucagon infusion (150 mug/h) into normal sheep, 2) glucagon infusion (100 mug/h) into insulin-treated alloxanized sheep, 3) insulin infusion (1.17 U/h) into normal sheep, and 4) insulin plus glucose infusion (12.3 mmol/h) into normal sheep. The second group of experiments was performed to prevent reflex hyperinsulinemia, and the fourth was performed to prevent reflex hyperglucagonemia. Glucagon directly stimulated the net hepatic uptake of alanine, glycine, glutamine, arginine, asparagine, threonine, serine, and lactate. Glucagon also stimulated lipolysis in adipose tissue. Insulin, on the other hand, appeared to have a lipogenic effect on adipose tissue and to stimulate directly the uptake of valine, isoleucine, leucine, tyrosine, lysine, and alanine only at extrahepatic sites. The study showed that, in sheep, the effects of glucagon primarily are on liver, and insulin's effects primarily are on skeletal muscle and adipose tissue where it promotes protein and lipid synthesis.