ENDOGENOUS RENAL TRANSPORT OF FREE AMINO ACIDS IN INFANCY AND CHILDHOOD

PEDIATRICS ◽  
1968 ◽  
Vol 42 (3) ◽  
pp. 395-404 ◽  
Author(s):  
Johannes Brodehl ◽  
Karl Gellissen ◽  
Annemarie Jäkel
Keyword(s):  
Amino Acids ◽  
Glomerular Filtration Rate ◽  
Urinary Excretion ◽  
Glomerular Filtration ◽  
Free Amino Acids ◽  
Free Amino ◽  
Filtration Rate ◽  
Tubular Reabsorption ◽  
Renal Transport ◽  
Clearance Rates

Endogenous renal transport of free amino acids was determined in 12 infants, between the ages of 16 days and 4 months, and in 12 children, between 2 and 13 years of age. Values of the serum concentrations, urinary excretion, renal clearance rates, net tubular reabsorption, and percentage tubular reabsorption of 17 amino acids were obtained by short-term clearance studies, including the determination of the glomerular filtration rate by inulin. The amino acids were determined by ion exchange chromatography. A comparison of the values of infants and children revealed a specific feature of the kidney function in infancy. The urinary excretion of threonine, serine, proline, glycine, and alanine and the clearance rates of serine, proline, glycine, and alanine were significantly higher in infancy. The percentage tubular reabsorption of all amino acids was characteristically lower in infancy than in childhood, while the values of the net tubular reabsorption related to the glomerular filtration rate (TAA/CIn) were equal in both groups. These findings are thought to be due to a greater degree of heterogeneity of nephrons with increased glomerulotubular imbalance during the period of postnatal kidney development.

The Relation between the Urinary Excretion of Inorganic Phosphate and Sodium

1971 ◽  
Vol 41 (3) ◽  
pp. 249-256 ◽  
Author(s):  
M. Fulop ◽  
P. Brazeau
Keyword(s):  
Glomerular Filtration Rate ◽  
Sodium Chloride ◽  
Urinary Excretion ◽  
Glomerular Filtration ◽  
Sodium Excretion ◽  
Inorganic Phosphate ◽  
Filtration Rate ◽  
Tubular Reabsorption ◽  
Back Pressure

1. The relation between the urinary excretion of inorganic phosphate and sodium was studied in anaesthetized dogs subjected to acute unilateral increases of ureteral back-pressure while receiving infusions of iso-osmotic sodium chloride. Under these circumstances modest increases of ureteral back-pressure, +14 to +23 cmH2O, were associated with relatively small changes of glomerular filtration rate from control values (−12.7 to +8.2%). 2. Increased ureteral back-pressure caused closely proportionate decreases of urinary phosphate and sodium excretion regardless of whether glomerular filtration rate increased, decreased or remained unchanged. When glomerular filtration rate increased or remained stable, the decreases of phosphate and sodium excretion were attributable to closely proportionate increases of tubular reabsorption of sodium and of phosphate. The increased tubular reabsorption of phosphate may be causally related to the increased tubular reabsorption of sodium.

Further Observations on the Response of the Glomerular Filtration Rate to Glucagon: Comparison with Secretin

1975 ◽  
Vol 53 (1) ◽  
pp. 81-85 ◽  
Author(s):  
Mortimer Levy
Keyword(s):  
Amino Acids ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Renal Denervation ◽  
Tubular Reabsorption ◽  
Left Renal Artery ◽  
Sodium Load ◽  
Small Doses ◽  
Compositional Changes

Glucagon causes marked elevations of glomerular filtration rate (GFR) in dogs when administered intravenously (i.v.) in small doses. The associated natriuresis is thought to be entirely due to increments in the filtered sodium load. In this study, renal denervation, thyroparathyroidectomy, and blockade of cholinergic, α- and β-adrenergic, dopaminergic and histaminergic receptors did not prevent the usual glucagon-induced elevations of GFR or rate of sodium excretion (UNaV). This effect of glucagon was not mediated through the release of cyclic AMP, or by plasma compositional changes of Ca2+, K+, or amino acids. Pure porcine secretin, in doses of 5–10 μg/min delivered either i.v. or into the left renal artery did not alter GFR; clearance rate of p-aminohippurate (CPAH) or UNaV in either hydropenic or saline-loaded dogs. Nor did this polypeptide, structurally very similar to glucagon, abolish the effect of glucagon on GFR. It did, however, partially inhibit the glucagon-induced natriuresis, presumably by preventing a previously undetected glucagon action on tubular reabsorption of sodium.

scholarly journals P27 The juvenile pig as animal model for unraveling renal drug elimination processes in children

2019 ◽  
Vol 104 (6) ◽  
pp. e28.1-e28
Author(s):  
L Dhondt ◽  
S Croubels ◽  
P De Paepe ◽  
P De Cock ◽  
M Devreese
Keyword(s):  
Animal Model ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Tubular Secretion ◽  
Tubular Reabsorption ◽  
Drug Elimination ◽  
Renal Drug Elimination

BackgroundOver the years pigs were promoted as potential animal model for humans due to their high degree of anatomical and physiological similarities with humans. Gasthuys et al. demonstrated that the maturation of the kidney function in terms of the glomerular filtration rate (GFR) in growing pigs was comparable to humans, but no data are currently available on renal plasma flow, renal tubular secretion and reabsorption.1 The aim of this pilot study was to unravel the contribution of distinct renal elimination processes in juvenile pigs and to compare with reported human values.MethodsEight seven-week-old pigs were intravenously administered a single bolus of a cocktail of following renal markers: iohexol (64.7 mg/kg body weight (BW), GFR), para-aminohippuric acid (PAH, 10 mg/kg BW, effective renal plasma flow (ERPF) and anion secretion), pindolol (0.05 mg/kg BW, cation secretion) and fluconazole (0.5 mg/kg, tubular reabsorption). Plasma and urinary concentrations were determined for PAH, pindolol and fluconazole at several time points. Only plasma concentrations were assessed for iohexol. PK modelling was performed with Phoenix® WinNonlin®.ResultsThe clearance of iohexol was 97.9 ± 16.1 ml/min/m² (mean ± SD). The ERPF, calculated as the renal clearance of PAH, was 9.5 ± 2.1 ml/min/kg. These GFR and ERPF values are approximately a factor 1.3 higher than the values observed in humans, namely 63.5–75.0 mL/min/m² and 6.5 ± 2.0 mL/min/kg.2,3 The net tubular secretion of PAH was 5.4 ± 1.8 mL/min/kg, which was comparable with the values obtained in humans (5.0 ± 1.8 mL/min/kg).3 Results for cation secretion and tubular reabsorption are not yet available (to be presented at the congress).ConclusionThe net tubular secretion of PAH was comparable between the juvenile pigs and humans. The GFR and ERPF were generally a factor 1.3 higher in juvenile pigs compared to humans.ReferencesGasthuys E., et al., Postnatal maturation of the glomerular filtration rate in conventional growing piglets as potential juvenile animal model for preclinical pharmaceutical research. Frontiers in Pharmacology 2017. 8.Schwartz GJ, Furth SL. Glomerular filtration rate measurement and estimation in chronic kidney disease. Pediatric Nephrology 2007;22(11):1839–1848.Gross AS, et al., Simultaneous administration of a cocktail of markers to measure renal drug elimination pathways: absence of a pharmacokinetic interaction between fluconazole and sinistrin, p-aminohippuric acid and pindolol. British Journal of Clinical Pharmacology 2001. 51(6):547–555.Disclosure(s)This study was funded by the Special Research Fund of Ghent University (BOF16/DOC/285).

MAXIMUM TUBULAR REABSORPTION CAPACITY OF GLUCOSE IN DIABETES MELLITUS

1965 ◽  
Vol 50 (1) ◽  
pp. 79-94 ◽  
Author(s):  
A. Vitelli ◽  
C. Cattaneo ◽  
P. F. Martini
Keyword(s):  
Diabetes Mellitus ◽  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Vascular Disease ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Normal Subjects ◽  
Tubular Reabsorption ◽  
Functional Changes ◽  
Two Factors

ABSTRACT The glomerular filtration rate (GFR) and maximum tubular reabsorption of glucose (TmG) were measured in 24 cases of diabetes mellitus. The patients, who were of different ages, varied with regard to the severity and duration of the disease and 11 patients showed clinical and functional evidence of vascular disease. The GFR and TmG were diminished in almost 50 per cent of cases, and the diminution of the two factors was closely correlated. The incidence of these renal functional changes was almost the same in the group of diabetics with vascular disease as in the group without complications. The GFR and TmG were not correlated with the age of the patients or with the severity of diabetes, though these factors were to some extent correlated with the duration of the disease. No relationship was observed between the incidence of impairment of the renal function and sex. The examinations carried out in this series of cases as well as in a number of normal subjects suggest various considerations with regard to the value of the various techniques which have been proposed for the measurement of the TmG.

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