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PubMed1989

Technetium-99m labeled p-aminohippuric acid analogues: renal function agents.

A number of p-aminohippuric acid analogues were synthesized in order to develop clinically useful 99mTc-labeled radiopharmaceuticals for evaluation of renal function measurements. Stable 99mTc-labeled complexes were formed at pH 5.7 using a Sn(II) reduction method with all derivatives. The newly synthesized complexes were screened utilizing biodistribution studies in small animals. All complexes were excreted via the GU tract within 60 min post iv administration, with no significant activity in GI tract and liver. The [99mTc]methyl-PAHIDA complex showed optimal biodistribution among these analogues. Further investigation is needed to determine if these derivatives may be used to replace [131I]o-iodohippuric acid for the evaluation of renal function.

Aminohippuric Acids↗
PubMed1977

Effect of splanchnicotomy on the renal excretion of para-aminohippuric acid in the anaesthetized dog.

Renal excretion of para-aminohippuric acid (PAH) was studied during PAH loading on unilaterally splanchnicotomized ("denervated") anaesthetized dogs. Urine flow, sodium excretion of denervated kidneys were significantly increased. Below a plasma concentration of 20 mg% there were no differences between intact and denervated kidneys in urinary excretion and in calculated tubular transport of PAH. However, maximum secretion rate on the splanchnicotomized side was significantly decreased (innervated: 34.8, denervated: 25.2 mg/100 ml GFR, respectively). Although both Na reabsorption and PAH secretion are impaired by denervation, the exact mechanism of action of renal sympathectomy is not elucidated as yet.

Aminohippuric Acids↗
PubMed1978

Maturation of p-aminohippuric acid transport in the developing rabbit kidney: interrelationships of the individual components.

The excretion of both endogenous organic (aryl) acids, such as benzoic acid, and exogenous ones, such as p-aminohippuric acid (PAH), penicillin, and furosemide, is reduced in the human neonate and other immature animals. The unique developmental pattern of aryl acid transport in immature rabbit kidney cortex slices is produced by the interrelationships of PAH uptake, efflux, and amount of intracellular binding protein, all of which reach mature levels at different ages.

Aminohippuric Acids↗
PubMed1977

Stimulatory and inhibitory effects of sulfhydryl reagent on p-aminohippuric acid transport by isolated renal tubules.

Isolated tubules from rabbit kidney cortex were treated with several different sulfhydryl reagents in an attempt to determine whether sulfhydryl groups are involved in organic acid transport. Disulfide reagents such as sodium tetrathionate and 6,6'-dithionicotinic acid were found to exert a biphasic effect on p-aminohippuric acid transport, i.e. transient stimulation followed by inhibition. In contrast, treatment of tubules with the mercaptide-forming reagent, p-chloromercuribenzoate, caused only inhibition of organic acid transport. Treatment of tubules with reductants such as dithiothreitol or mercaptoethanol blocked the stimulatory effect of tetrathionate without affecting the inhibitory effect of this oxidant. The inhibition caused by p-chloromercuribenzoate, however, was largely reversible when tubules were treated with reductants. The results suggest that the renal organic acid transport system contains sulfhydryl groups and that its activity is increased when some of these groups are oxidized.

Animals↗
PubMed1979

The transport of para-aminohippuric acid by the ciliary body and by the iris of the primate eye.

Para-aminohippuric acid (PAH) accumulates against a concentration gradient in the ciliary body and independently in the iris of the rhesus monkey eye. This accumulation is inhibited by incubation of 0 degrees C and shows saturation kinetics in both tissues. Cyanide, ouabain, dinitrophenol, iodopyracet, and probenecid effectively depress PAH uptake in both tissues, but anaerobic incubation conditions have little effect on uptake in either tissue. The washout of preaccumulated PAH occurs 2.5 times faster from the iris than from the ciliary body. The effects on washout of 10(-4)M PAH, 0 degrees C, and 10(-5)M dinitrophenol are consistent with washout occurring by a diffusional mechanism in both tissues, with some reaccumulation occurring in the ciliary body only. In addition, nonsaturable uptake of PAH, studied in both tissues under high PAH concentrations, also occurs significantly faster in the iris than in the ciliary body. The kinetic analysis of active PAH uptake in both tissues is discussed in terms of initial uptake and in terms of a steady-state model. This steady-state model compensates for some technical problems in applying in vitro incubation techniques to primate tissues and also includes a correction for the additional exchange processes that affect the two tissues differently. Results of the kinetic analysis suggest that, at least to an order of magnitude, iris uptake is significant with respect to ciliary body uptake.

Aminohippuric Acids↗
PubMed1985

Effects of the diuretic torasemide on p-aminohippuric acid transport in the rat.

The effect of torasemide, a new diuretic, on p-aminohippuric acid (PAH) transport (TPAH) was studied using renal clearance and micropuncture techniques in anaesthetized rats. In clearance experiments, TPAH and TPAH/glomerular filtration rate (GFR) did not significantly change after i.v. administration of torasemide or furosemide but decreased after probenecid injection. In order to enhance the possibility to demonstrate torasemide and PAH interference, small volumes of [3H]-PAH + [14C]-inulin solutions were directly injected into the peritubular capillary system using calibrated micropipettes. When the concentration of microinjected PAH was less than or equal to 0.6 mmol/l, fractional recovery of [3H]-PAH from the micropunctured kidney was not significantly decreased by the diuretics in contrast to probenecid. When the concentration of microinjected PAH was greater than or equal to 5 mmol/l, fractional recovery of [3H]-PAH from the micropunctured kidney was significantly decreased by torasemide from 252% (control) to 210% (P less than 0.005), by furosemide to 217% (P less than 0.005), and by probenecid to 205% (P less than 0.01). Under these conditions, differential transit times between [3H]-PAH and [14C]-inulin in the micropunctured kidney were decreased from -15 to -4 s in the presence of torasemide (P less than 0.05). They were slightly but not significantly reduced by furosemide and probenecid. These findings suggest interference, at least to some extent, between torasemide and PAH secretion in the rat kidney.

Aminohippuric Acids↗
PubMed2001

Simultaneous determination of inulin and p-aminohippuric acid in plasma and urine by reversed-phase high-performance liquid chromatography.

A simple, accurate and sensitive high-performance liquid chromatographic method with UV detection was carried out to measure simultaneously plasma and urine concentrations of both p-aminohippuric acid and inulin. Following a simplified acid hydrolysis of the sample, the separation was carried out in 4 min using a C18 reversed-phase column with a flow-rate of 1 ml/min, and monitoring the absorbance at 280 nm. Within the investigated concentration ranges of inulin (0.1-3.2 mg/ml) and p-aminohippuric acid (0.0097-0.3 mg/ml), good linearity (r>0.99) was obtained. Within-run RSD ranged from 2.9 to 6.1% and between-run RSD ranged from 6.4 to 10%. Analytical recoveries were 101-112%, with little differences between plasma and urine samples. The detection limit was 1 microg/ml for all the analytes studied. This method might be ideal for renal function studies where a rapid and reproducible assessment of both renal glomerular filtration rate and blood flow-rate is required.

Adult↗
PubMed1981

Effect of unconjugated bilirubin on the uptake of p-aminohippuric acid by the isolated perfused rat kidney.

The effect produced by unconjugated bilirubin (UB) on p-aminohippuric acid (PAH) translocation from plasma to the urine, was analyzed by using an isolated rat kidney preparation applying the multiple indicator dilution technique. Arterial -to- urine mean transit times and fractional recoveries of creatinine and PAH in the venous effluent, were calculated before and after the incorporation of UB into the system. PAH influx into cells, its efflux from the cells to the capillaries, and its movement between lumen and tubular cells were also calculated. The results indicated that PAH influx into cells was impaired in the presence of UB. The phenomenom was shown to be dose-dependent. On the contrary, the efflux of PAH to the capillaries that was also impaired by UB, seemed to be unrelated to the pigment concentration within the system. Movement of PAH between lumen and tubular cells also appeared to be affected by UB. The results obtained suggested that UB interferes with the renal handling of PAH but the mechanism involved could not be clarified with the model used.

Aminohippuric Acids↗
PubMed1988

Chemical assay of p-aminohippuric acid simplified by use of dimethylaminocinnamaldehyde in ethanol.

We have developed a new and simple method of p-aminohippuric acid determination by use of dimethylaminocinnamaldehyde (DACA). It differs from previous methods using DACA in that the reaction is carried out in ethanol rather than in dilute acid. This results in deeper and more stable color development. We have used this method successfully to determine effective renal plasma flow in a clinical study of this variable in pregnant women.

Aminohippuric Acids↗
PubMed2005

Clearance of para-aminohippuric acid in wethers consuming locoweed.

AIM: To validate the use of para-aminohippuric acid (PAH) as a marker for measuring blood flow in wethers consuming a mixed diet of locoweed and blue grama hay. METHODS: Fourteen sheep, stratified by bodyweight (BW), were assigned to one of three treatments: 0.8 mg swainsonine (SW)/kg BW (HI), 0.2 mg SW/kg BW (LO), and no SW (Control). Sheep were fed various ratios of locoweed and blue grama hay to deliver SW treatments, for 28 days prior to infusion of PAH. Concentrations of SW and activities of alkaline phosphatase (Alk-P) and aspartate aminotransferase (AST) in serum were measured to confirm exposure to SW and subclinical intoxication. A single 20-ml injection of 5% PAH was delivered into the jugular vein after subclinical intoxication had been achieved. Blood samples were collected and serum analysed for PAH immediately prior to injection, then every 5 min from 5-30 min, and every 10 min from 30-60 min, following injection of PAH. RESULTS: Effective delivery of SW was evident from the greater concentrations of SW measured in the serum of HI compared with LO animals (p<0.05). No significant differences were detected in the rate of elimination (range 0.097-0.108 L/min), elimination half-life (range 6.62-7.24 min), apparent volume of distribution for the central compartment (range 7.14-9.72 L), and clearance (range 0.73-0.92 L/min) of PAH, between treatments. CONCLUSIONS: Subclinical intoxication with SW did not affect the pharmacokinetics of PAH. Thus, use of downstream dilution of PAH is a valid method to determine the rate of blood flow in nutrient flux experiments that involve consumption of locoweed.

Alkaline Phosphatase↗
PubMed1977

[Concentration of p-aminohippuric acid in the serum and kidney tissue during stimulation of renal excretion of foreign materials].

The renal excretion of p-aminohippuric acid (PAH) can be stimulated in adult rats by repeated applications of probenecid, cyclopenthiazide, and phenobarbital. The present studies have shown that this pretreatment significantly shortens the half-life for PAH too. In pretreated animals the PAH concentration decreases in the renal tissue more rapidly than in the control animals. These results were obtained in adult animals only but not in 5-day-old rats, in which the pretreatment had no effect upon the rate of renal PAH excretion. The pretreatment did not change the renal weight of 5-and 55-day-old rats.

Aminohippuric Acids↗
PubMed1999

99Tcm-p-aminohippuric acid as a new renal agent.

99Tcm-p-aminohippuric acid (99Tcm-PAH) is a new renal radiopharmaceutical prepared from a lyophilized kit by the addition of sodium pertechnetate (Na99TcmO4). Each vial contains PAH, the calcium trisodium salt of diethylenetriamine pentaacetic acid (CaNa3DTPA) and stannous chloride (SnCl2.2H2O) in an inert atmosphere. It is a stable radiopharmaceutical with high radiochemical purity (> 95%). Its protein binding is very similar to that of 131I-OIH, but it is hydrophilic in character. Animal studies using 99Tcm-PAH have indicated that it provides renal images of satisfactory quality with no external background. Despite its almost identical radiochemical purity and HPLC analysis results to 99Tcm-DTPA, 99Tcm-PAH is rapidly secreted by the kidneys in a manner consistent with tubular secretion, as confirmed by rat probenecid studies, whereas 99Tcm-DTPA is excreted by glomerular filtration. The pharmacokinetic parameters of 99Tcm-PAH (t1/2(alpha)) = 2.5 min, t1/2(beta) = 41.7 min, Cl = 5.22 ml.min-1, Kel = 5.1 x 10(-4) min-1) differ from those of 99Tcm-DTPA. Evaluation of 99Tcm-PAH in two human volunteers confirmed its good renal characteristics: rapid disappearance from the vascular system, high uptake in kidneys followed by its very fast elimination, and low residual activity 20 min after its intravenous administration.

Animals↗
PubMed2004

A new HPLC method to determine glomerular filtration rate and effective renal plasma flow in conscious dogs by single intravenous administration of iohexol and p-aminohippuric acid.

A high-performance liquid chromatography method to determine iohexol (IOX) and p-aminohippuric acid (PAH) in the plasma of dogs is evaluated according to recovery, reproducibility, and linearity utilizing a gradient pump. The mobile phase consists of 50mM sodium dihydrogen phosphate with 0.5mM tetrabutylammonium chloride, the pH is adjusted to 4.1, methanol is added to the final ratio of 90:10 (v/v), the flow rate is set at 1 mL/min, and separation is achieved with an ODS2 Luna column. The UV detector is set at 254 nm. IOX and PAH are used for evaluation of the effective renal plasma flow (ERPF) and glomerular filtration rate (GFR). The present method tested in three dogs demonstrates the accuracy in the evaluation of ERPF and GFR. Because of its precision and simplicity and low cost, it can be considered a good tool for ERPF and GFR in small animal practice.

Animals↗
PubMed1975

Passage of inulin and p-aminohippuric acid through artificial membranes: implications for measurement of renal function.

Diffusion of inulin and p-aminohippuric acid (PAH) in combined aqueous solution through artificial membranes was measured at room temperature and atmospheric pressure. The membranes had pore diameters of 26, 50, 100, 200, 250, 350, 510 or 990 A. The diffusion of PAH was only restricted with a pore size of 26 A, but inulin diffusion was restricted at 100 A. When diffusion of both solutes was unrestricted (pore diameter greater than or equal to 200 A), PAH diffused four times faster than inulin, and in restricted situations this ratio was even greater. The results of these diffusion studies allow the major and minor molecular dimensions of the solutes to be estimated. Filtration of the two solutes was studied in slowly flowing situations and also with increased temperature and pressure. Pore sizes required for unrestricted filtration were the same as for unrestricted diffusion but the passage ratio was reduced from 4 to 2. These results suggest strongly that two conditions are necessary if the glomerular filtration rate (GFR) of inulin is to equal the true GFR: membrane pore size must be at least 200 A and passage through the membranes must be by bulk transport.

Aminohippuric Acids↗
PubMed2001

Alternative high-performance liquid chromatographic assay for p-aminohippuric acid (PAH): effect of aging on PAH excretion in the isolated perfused rat kidney.

Para-aminohippuric acid (PAH), an indicator of renal plasma flow, is a commonly used marker of organic anion transport by the kidney. An analytical method for PAH using HPLC was developed. The method is simple, fast and requires a minimum amount of organic solvent. Sample preparation involved protein precipitation with zinc sulfate. Para-amino benzoic acid was utilized as an internal standard (IS). Chromatography was performed using a reversed-phase phenyl column with UV detection at a wavelength of 254 nm. Mobile phase consisted of 0.1 M acetic acid and acetonitrile (99:1) at a flow rate of 1 ml/min. The assay was validated over a standard concentration range from 1 to 25 microg/ml. Accuracy, precision, reproducibility and specificity of the method was established with coefficients of variation <10%. The method was sensitive and showed linear response in peak height ratio (analyte:IS) over the concentration range studied (r(2)>0.99). The assay was used to study the effect of aging on PAH excretion in the isolated perfused rat kidney model. Experiments were conducted in kidneys from young (2-3 months, n=6), adult (6-9 months, n=5) and aged (12-16 months, n=3) male Sprague-Dawley rats at an initial drug concentration of 20 microg/ml. Significant differences in kidney function (e.g. glomerular filtration rate and glucose reabsorption) were observed in aged kidneys. Despite a 5-fold reduction in glomerular filtration rate, PAH renal clearance (kidney weight-corrected) decreased by only 2-fold in aged (2.2+/-0.42 ml/min per gram) compared to young (4.6+/-0.70 ml/min per gram, P<0.05) rats. Furthermore, renal excretion ratio was significantly higher in aged rats (27+/-8.0 vs. 15+/-5.0, P<0.05). These preliminary findings challenge the 'Whole Nephron Hypothesis' that assumes parallel reductions in renal filtration and secretory capacity secondary to disease or aging.

Aging↗
PubMed1987

Indirect coupling to Na+ of p-aminohippuric acid uptake into rat renal basolateral membrane vesicles.

Experiments with basolateral membrane vesicles prepared from rat kidney cortex were performed to study the mechanism by which p-aminohippuric acid (PAH) is taken up across the contraluminal membrane and is concentrated in proximal tubule cells. An inward Na+ gradient failed to stimulate [3H]PAH uptake compared with K+ or Li+ and did not cause intravesicular PAH accumulation above equilibrium distribution. In the absence of Na+, the dicarboxylates glutarate and suberate cis-inhibited and trans-stimulated [3H]PAH uptake, indicating a common transport system. In the presence of Na+, 10 microM glutarate in the incubation medium did not cis-inhibit, but rather stimulated [3H]PAH uptake and caused PAH accumulation above equilibrium distribution ("overshoot"). Li+ diminished this stimulation, but was without effect on [3H]PAH/PAH- and [3H]PAH/glutarate exchange. The data indicate the coexistence of a Na+ -coupled, Li+-sensitive transport system for dicarboxylates and a Li+ -insensitive PAH/dicarboxylate exchanger in the basolateral membrane. We propose that dicarboxylates are cotransported with Na+ into the cell and subsequently exchange for extracellular PAH at the basolateral membrane. PAH uptake is thereby indirectly coupled to Na+ via the Na+/dicarboxylate cotransporter.

Aminohippuric Acids↗