title: Role of blood cells in leucine kinetics across the human kidney.
abstract: To evaluate the role of blood cells in interorgan amino acid transport and in the estimates of regional protein turnover, we studied the effects of plasma vs. whole blood sampling on regional leucine kinetics in postabsorptive humans. Studies were carried out by combining the arteriovenous difference technique with the measurement of [14C]- and [15N]leucine isotope exchange across the human kidney, the splanchnic area, and the leg. In the kidney, whole blood-derived rates of leucine-carbon appearance, disappearance, and net balance (NB) were greater (by 3-15 times; P < 0.035) than those calculated in plasma. In addition, the net leucine-carbon (i.e., protein) balance across the kidney was negative in whole blood (-5.6 +/- 1.3 micromol/min x 1.73 m2, P < 0.01 vs. 0) but neutral in plasma [-0.24 +/- 1.33, P = not significant from 0; P < 0.01 vs. whole blood]. A net leucine transport out of renal cells was shown in blood but not in plasma. In contrast, rates of leucine-carbon appearance, disappearance, NB, and net transport, in both the splanchnic area and the leg, were similar in whole blood and plasma. These data suggest that blood cells play a key role in leucine transport out of the kidney and, consequently, in the leucine-derived estimates of renal protein degradation and NB, which is at variance with what is observed across the splanchnic organs or the leg. These data also emphasize the need for complete whole blood arteriovenous measurements to accurately estimate protein turnover across the kidney.
authors.affiliation: Nephrology Division, Department of Internal Medicine, University of Genoa, 16132 Genoa. gari@unige.it
authors.forename: Giacomo
authors.initials: G
authors.lastname: Garibotto
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Russo
authors.forename: Antonella
authors.initials: A
authors.lastname: Sofia
authors.forename: Monica
authors.initials: M
authors.lastname: Vettore
authors.forename: Laura
authors.initials: L
authors.lastname: Dertenois
authors.forename: Cristina
authors.initials: C
authors.lastname: Robaudo
authors.forename: Giacomo
authors.initials: G
authors.lastname: Deferrari
authors.forename: Michela
authors.initials: M
authors.lastname: Zanetti
authors.forename: Paolo
authors.initials: P
authors.lastname: Tessari
mesh_terms: D000328:Adult; D001692:Biological Transport / Q000502:physiology; D001773:Blood Cells / Q000502:physiology*; D005260:Female; D005263:Femoral Artery; D005268:Femoral Vein; D006801:Humans; D007651:Keto Acids / Q000097:blood; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D007930:Leucine / Q000097:blood / Q000493:pharmacokinetics*; D008297:Male; D011506:Proteins / Q000378:metabolism; D013152:Splanchnic Circulation
chemical_list: D007651:Keto Acids; D011506:Proteins; C013082:alpha-ketoisocaproic acid; D007930:Leucine