Para-aminohippuric acid

Explain how plasma clearance of para-aminohippuric acid is used to determine the effective renal plasma flow... 

A substance that fulfills these criteria is para-aminohippuric acid (PAH). All of the PAH not filtered at the glomerulus is secreted by the proximal tubule. The net effect is that all of the plasma flowing through the nephrons is completely cleared of PAH. It is important to note that about 10 to 15% of the total renal plasma flow supplies regions of the kidneys that are not involved with filtration or secretion. Consequently, this plasma cannot be cleared of PAH. Therefore, the plasma clearance of PAH provides a measurement of the effective renal plasma flow, that is, the volume of plasma that actually flows through the nephrons. The ERPF is normally about 625 ml/ min. (This value is based on a renal blood flow of about 1.1 1/min and a hematocrit of about 42.)... 

Another model substance that is used experimentally for the assessment of kidney function is para-aminohippuric acid (p-AH). p-AH appears in the urine not just by filtration but mainly by active secretion in the proximal tubule. This active transport process occurs in two steps (Figure 2.19a) In the first step, p-AH is exchanged at the basolateral membrane of the proximal tubule cell against a-ketoglutarate or other divalent anions. This exchange is driven by the membrane potential (the interior of the tubule cell is electrically negative relative to the outside, as is the case with essentially all cells). 

Platelet-activating factor Para-aminohippuric acid Percutaneous acetic acid injection Punction/Aspiration/Injection/Re-Aspiration Perinuclear antineutrophihc cytoplasmic antibody... 

Diatrizoate can interfere with para-aminohippuric acid extraction studies (SEDA-15, 502) (321). 

Renal accumulation is unaffected by probenecid and para-aminohippuric acid (PAH) (Lee and Blaufox 1985). Uptake is decreased by ACE inhibitors in the presence of renal artery stenosis (Hovinga et al. 1989 Kopecky et al. 1990). 

In vivo experiments were performed using para-aminohippuric acid (PAH) as a marker inside the polymers. Data of rats PAH concentration in the urine after implantation showed that the PAH concentration in the urine was pronounced during the exposure and mainly in the timespan just after the exposure. The delay was presumably the diffusion time from the implantation site to the bloodstream and then the removal by the kidneys. When control animals were treated by the same procedure, i.e., placing the ultrasonic applicator head over the treated area with the power level of the ultrasound set to zero, no effect of the ultrasound could be detected... 

Plasma clearance of para-aminohippuric acid (PAH) is almost equal to a plasma flow. 

An indirect measurement of RBF can be made using para-aminohippuric acid (PAH) clearance. This molecule is an ideal marker of the effective renal plasma flow (eRPF), as it freely filters through the glomerulus, and any amotmt remaining in the peritubular capillary plasma is secreted into the proximal tubule. Therefore, essentially aU PAH passing through the kidneys appears in the urine. For this reason, the PAH clearance is directly proportional to the rate of plasma flow through the kidneys. If the hematocrit is known, the total renal blood flow can be easily calculated from the eRPF value. 

K. J. Ullrich, G. Rumrich, T. Wieland, and W. Dekant, Contraluminal para-aminohippurate (PAH) transport in the proximal tubule of the rat kidney VI Specificity Amino acids, their N-methyl-, N-acetyl-, and W-benzoylderiva-tives glutathione- and cysteine conjugates, di- and oligopeptides, Pflugers Arch., 415 342-350 (1989). 

Exhibiting a pattern of eicosanoid excretion noted in essential hypertension, lead-exposed workers showed an increase in TxB2 and a decrease in PGE2 and 6-keto-PGF] in fhe mine [63]. In contrast to the reabsorpfive defect of acute lead nephropathy, saturnine gout is characterized by renal retention of uric acid. The clearance and maximal secretion rate for para-aminohippurate have been found to be variable in patients with occupational lead nephropathy. A reduced maximal reabsorpfive rate for glucose has been reported, but simultaneous, matched controls were not obtained [69]. 

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