Characteristics of p-aminohippurate transport in proximal renal tubules

Tune, BM; Burg, M. B.; Patlak, C. S.

doi:10.1152/ajplegacy.1969.217.4.1057

Cited by 195 publications

(59 citation statements)

References 2 publications

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“…Endogenous creatinine clearance -and accordingly glomerular filtration rate -decreases with age at a rate approximately 1% per year after 40 y (Lubran, 1995). PABA metabolites are also excreted by active tubular secretion (Tune et al, 1969), which also decreases with age. Thus, reduced 24 h PABA recovery with increasing age could be caused by a delayed renal clearance due to these reductions in the functions of the aging kidneys, as has been demonstrated for other water-soluble drugs mostly cleared by the kidneys (Lobel & Bergeron, 1987).…”

Section: Discussionmentioning

confidence: 99%

Para-aminobenzoic acid (PABA) used as a marker for completeness of 24 hour urine: effects of age and dosage scheduling

2003

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Objective: To examine the age dependency of the urinary para-aminobenzoic acid (PABA) excretion, and if a delayed PABA excretion can be overcome by advancing intake schedule; and to examine the recovery of PABA in fractionated urinary samples collected during 24 h after single and repeated doses of PABA. Design: Cross-over study with subjects randomized to start with recommended schedule of PABA administration (80 mg at 08:00, 12:00 and 18:00; PABA18) and then an advanced schedule (80 mg at 08:00, 12:00 and 15:00; PABA15) or vice versa. One subgroup of eight subjects collected individual urine specimens for 24 h after a morning dose of 80 mg of PABA, and another subgroup of 10 subjects collected individual urine specimens for 24 h after ingestion of 80 mg of PABA three times at mealtimes. Subjects: Employees and relatives from the Danish Food Administration. Setting: Ninety-nine healthy volunteers (61 females and 38 males) aged 30 -91 y. Results: Linear regressions for PABA15 and PABA18 demonstrate significantly less recovery with age (PABA15: r 2 ¼ 0.1784, P ¼ 0.0002; PABA18: r 2 ¼ 0.1273, P ¼ 0.0019). Linear regression of DPABA (PABA15 -PABA18) with age showed the best fit line to be horizontal (slope 7 0.0066, P ¼ 0.89; 95% CI 7 0.1046, 0.0915) and with a Y-intercept not significantly different from 0 (1.575; 95% CI 7 4.176, 7.326). In this population the lower limit for complete 24 h urine collection was 79.2%. After a single dosage of 80 mg PABA 70 -85% was recovered after 8 h. Within 16 h after ingestion of 240 mg PABA at recommended hours the lowest acceptable recovery (78.1%) was reached. Conclusion: There is a gradual decline of PABA recovery with age that cannot be overcome by advancing the dosage schedule. Because of a lower delimiting PABA recovery for the elderly, some 24 h collections in this age group will be rejected unjustly (false-negatives). Also, with the currently recommended dosage schedule (PABA taken with the main meals) the risk of falsepositive 24 h urine collections prevails. With refinement of the PABA test procedure, ie employing a specific analytical method and age-dependent cut-off values, the test may achieve a higher specificity and sensitivity.

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Section: Discussionmentioning

confidence: 99%

Para-aminobenzoic acid (PABA) used as a marker for completeness of 24 hour urine: effects of age and dosage scheduling

2003

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“…In the slice system luminal space is presumably very low (Bojesen & Leyssac, 1965), and there is no concentration step between cell and lumen of proximal tubules (Tune, Burg & Patlak, 1969). Therefore accumulation of PAH in kidney slices may be presumed primarily to be located intracellularly and to represent the capability of the peritubular membrane for active transport of the organic anion.…”

Section: Discussionmentioning

confidence: 99%

An energy‐dependent, sodium‐independent component of active p‐aminohippurate transport in rabbit renal cortex.

Maxild¹,

Møller²,

Sheikh³

1981

The Journal of Physiology

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SUMMARY1. The relation between the coupling of metabolic energy to renal p-aminohippurate (PAH) accumulation and Na+-K+ transport was studied in rabbit cortical slices.2. Cyanide (CN-), 2,4-dinitrophenol (DNP) and fluoride (F-) at low-medium concentrations, giving rise to a slight decline of tissue ATP concentration, caused a reduction of PAH accumulation without significantly affecting intracellular Na+ and K+ concentrations. However, higher levels of the metabolic inhibitors also resulted in considerable inhibition of active Na+-K+ transport.3. The rate of carrier-mediated PAH uptake was slow under anaerobic conditions, relative to that measured under aerobic conditions in Na+-depleted slices. In the latter case the maximal accumulation achieved was only 1-55 + 0-16.4. The uptake rate of PAH under anaerobic conditions was not inhibited by the absence of Na+ or addition of metabolic inhibitors in the concentrations used under aerobic conditions. 5. It is concluded that although Na+ is required for the attainment of high accumulation ratios of PAH, oxidative metabolism stimulates PAH flux by a Na+-independent mechanism.

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“…PAH, an organic anion, is concentrated and secreted by the cells of the proximal tubule (25). The rate of secretion is higher in the straight than the convoluted portion (23). Transfer of PAH from peritubular capillary to lumen appears to occur in two steps.…”

Section: Speculationmentioning

confidence: 99%