Meeting Abstract

P1.105  Friday, Jan. 4  Egg laying hens produce artificially enriched ^13C proteins for tracer studies ARQUISOLA, B; ALBACH, B; MCCUE, M.D.*; St. Mary’s University mmccue1@stmarytx.edu

Physicians and researchers studying the physiology or pathophysiology of protein metabolism often use ¹³C-labled free amino acid tracers, which violates the assumption that a tracer molecule undergoes the identical biochemical reactions as the tracee molecule (i.e. proteins). The goal of this study was to investigate ¹³C-protein synthesis using a hen model (Gallus domesticus). Here we characterize the relationship between ¹³C-1-L-leucine dosing protocols (e.g., ¹³C-tracer dose response curve and ¹³C tracer mixed in food or dissolved in drinking water), describe the incorporation and washout kinetics of 13C tracers, and generate highly enriched ¹³C-egg white proteins (using a uniformly ¹³C-labeled mixture of amino acids). Recovery of ¹³C in egg whites ranged from 14% to 21% for the leucine and mixed amino acid tracers, respectively. At the highest leucine doses (434 mg day^-1) egg whites were over 150‰ above natural abundance. The cost of isotopic enrichment (δ^-1) was lower for the leucine tracer than the mixed amino acid tracers and was lowest at the smallest doses (86 mg day^-1). The time required for half maximal ¹³C enrichment (t₅₀) depended chiefly on the mode of tracer administration and ranged from 2.5 days to 4.9 days for ¹³C-leucine dissolved in water or mixed in the food, respectively. Uniformly ¹³C labeled amino acid tracers were lost from the body at a rate (t₅₀ = 3.0 days) nearly half of that of the rate of uptake (₅₀ = 1.7 days), indicating significant biochemical discrimination of ¹³C amino acids.