Intravenous Amino Acid Tolerance Studies in Humans.

Abstract

The rates of disappearance (tolerance) of 10 intraven. administered acids from the plasma as well as the concomitant excretion in the urine was studied in normal subjects. After a 12-hr. fast, blood samples were drawn for detn. of fasting levels. The amino acid mixture (VUJ-N, Merck) was then injected intraven. as rapidly as possible at a level of 1 ml/lb. body wt. Blood samples were then taken at 15, 30, 60, 120, and 180 min. after the injn., and urine excreted during the 2-hr. period immediately prior to the injn., as well as during the period when the bloods were taken, was also collected for assay. Ten amino acids were then determined microbiologically on the deproteinized plasma, and on the urines. At the 15-min. period of observation, the pattern of amino acids in the plasma was similar to that injected, but it was considerably altered in the later periods. Some differences in this alteration were noted when various subjects were compared. The pattern of amino acids excreted bore no relationship to that infused. At the infusion levels used in these expts., histidine, lysine, and threonine accounted for the majority of the urinary amino N measured.