Splanchnic uptake and oxidation of proljne in healthy subjects

To determine uptake of dietary pro by the splanchnic region in healthy humans, we conducted an experiment in 8 adults receiving an L-amino acid diet providing adequate nitrogen and energy intake for 10 days. On day 7, they received an 8h primed constant administration of L-[C]Pro and L-t5,5,2HJPro (3h fast;5fed) by the IV or oral routes, respectively. On day 10 the routes of administration were reversed. Pro fluxes with the [13C] pro tracer were 80±9.4 and 95±13 and 122±18 and 148±25 Itmol.kg'.h' ; (mean +. SD; fast and fed for IV and oral routes respectively); with pHJ pro, fluxes were higher, 118±12 and 131±14 and 165±18 and 166±7 (fast and fed for IV and oral routes respectively). Splanchnic uptake (fraction of tracer; mean .+ SD) was 0.34.+.0.08 and 0.35±0.12 for fast and fed, respectively, for [CJ pro; and 0.28±0.09 and 0.17±0.08 for the [₂H₂] pro. Pro oxidation was different for the fed and fast state and 13.2±1 and 27.5±3.4 /unol.kg-'.h-' with [¹³C] pro given IV, similar rates were found with the oral [¹³C] tracer. [¹³C] labeling of plasma cit was greater than orn; labeling was higher with oral [¹³C]pro. The [³H₂] pro tracer did not give rise to labeled om or cit. The findings will be discussed in relation to the splanchnic metabolism of urea cycle intermediates.