title: Tubular function by lithium clearance, plasma amino acids and hormones following a meat meal in childhood.
abstract: Tubular function was measured by lithium clearance (CLi) and by its derived formulae before and after the transient increase (lasting 90 min) in glomerular filtration rate (GFR) following a meat meal (2g protein/kg body weight) in 12 normal children. Three baseline and 4 clearances after the meal were obtained, each lasting 30 min. The mean baseline CLi was 23.1 +/- 1.64 ml/min/1.73 m2. At peak GFR response (60 min from starting the meal), CLi averaged 27.6 +/- 2.4 ml/min/1.73 m2 (p less than 0.025 vs. baseline) and it was further increased (32.2 +/- 5.04 ml/min/1.73 m2, p less than 0.01 vs. baseline) 120 min after starting the meal, while GFR returned to baseline values. Fractional lithium excretion averaged 0.23 +/- 0.04 at baseline and increased continuously after the meat meal and, at completion of the study, it averaged 0.38 +/- 0.07 (p less than 0.025 vs. baseline). The distal absolute and fractional sodium reabsorption increased throughout the studies following the meal and peaked at 120 min. The functional changes were associated with a statistically significant increase in the plasma concentration of insulin, glucagon, and total amino acids after the meal. The latter at the end of the study was almost doubled (5,600 +/- 780 versus 3,200 microM at baseline, p less than 0.01). The data indicate that the tubulo glomerular feedback mechanism operates normally after a meat meal. The finding on increased distal sodium reabsorption might point to the existence of an insulin-dependent mechanism.
authors.affiliation: Department of Pediatrics, Federico II University, Naples, Italy.
authors.forename: N G
authors.initials: NG
authors.lastname: De Santo
authors.forename: S
authors.initials: S
authors.lastname: Coppola
authors.forename: G
authors.initials: G
authors.lastname: Coscarella
authors.forename: P
authors.initials: P
authors.lastname: Anastasio
authors.forename: G
authors.initials: G
authors.lastname: Capasso
authors.forename: L
authors.initials: L
authors.lastname: Bellini
authors.forename: G
authors.initials: G
authors.lastname: Spagnuolo
authors.forename: P
authors.initials: P
authors.lastname: Strazzullo
authors.forename: A
authors.initials: A
authors.lastname: Lombardi
authors.forename: R
authors.initials: R
authors.lastname: De Mercato
mesh_terms: D000450:Aldosterone / Q000097:blood; D000596:Amino Acids / Q000097:blood*; D002648:Child; D004044:Dietary Proteins; D005260:Female; D005919:Glomerular Filtration Rate; D005934:Glucagon / Q000097:blood; D013006:Growth Hormone / Q000097:blood; D006400:Hematocrit; D006728:Hormones / Q000097:blood*; D006801:Humans; D007328:Insulin / Q000097:blood; D007684:Kidney Tubules / Q000502:physiology*; D008094:Lithium / Q000378:metabolism; D008297:Male; D008460:Meat; D008657:Metabolic Clearance Rate; D012079:Renal Circulation; D014655:Vascular Resistance
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D006728:Hormones; D007328:Insulin; D000450:Aldosterone; D013006:Growth Hormone; D005934:Glucagon; D008094:Lithium