Determination of inulin in plasma and urine by reversed-phase high-performance liquid chromatography

A structural and spectroscopic study on para-aminohippuric acid with experimental and theoretical approaches

In this work, the molecular conformation, vibrational and electronic analysis of para-aminohippuric acid (pAHA, C(9)H(10)N(2)O(3)) were presented for the ground state using experimental techniques (FT-IR, FT-Raman and UV) and density functional theory (DFT) employing B3LYP exchange correlation with the 6-311++G(d,p) basis set. FT-IR and FT-Raman spectra were recorded in the regions of 400-4000cm(-1) and 50-4000cm(-1), respectively. The UV absorption spectra of the compound that dissolved in ethanol and water solution were recorded in the range of 190-400nm. Potential energy curve was computed by means of scanning NCCO torsion angle. The geometry optimization and the energies associated possible four conformers (C1-C4) were computed. The computational results diagnose the most stable conformer of pAHA as the C1 form. Optimized structure of compound was interpreted and compared with the earlier reported experimental values. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. A study on the electronic properties, such as frontier molecular energies, absorption wavelengths and oscillator strengths, were predicted by time-dependent DFT (TD-DFT) approach, while taking solvent effects into account. To investigate non-linear optical properties: polarizability, anisotropy of polarizability and molecular first hyperpolarizability of molecule were computed. Thermodynamic properties (heat capacity, entropy and enthalpy) of the title compound at different temperatures were calculated.

Dextran fractional clearance studies in acute dengue infection

Background

Although increased capillary permeability is the major clinical feature associated with severe dengue infections the mechanisms underlying this phenomenon remain unclear. Dextran clearance methodology has been used to investigate the molecular sieving properties of the microvasculature in clinical situations associated with altered permeability, including during pregnancy and in various renal disorders. In order to better understand the characteristics of the vascular leak associated with dengue we undertook formal dextran clearance studies in Vietnamese dengue patients and healthy volunteers.

Methodology/Principal Findings

We carried out serial clearance studies in 15 young adult males with acute dengue and evidence of vascular leakage a) during the phase of maximal leakage and b) one and three months later, as well as in 16 healthy control subjects. Interestingly we found no difference in the clearance profiles of neutral dextran solutions among the dengue patients at any time-point or in comparison to the healthy volunteers.

Conclusions/Significance

The surface glycocalyx layer, a fibre-matrix of proteoglycans, glycosaminoglycans, and plasma proteins, forms a complex with the underlying endothelial cells to regulate plasma volume within circumscribed limits. It is likely that during dengue infections loss of plasma proteins from this layer alters the permeability characteristics of the complex; physical and/or electrostatic interactions between the dextran molecules and the glycocalyx structure may temporarily restore normal function, rendering the technique unsuitable for assessing permeability in these patients. The implications for resuscitation of patients with dengue shock syndrome (DSS) are potentially important. It is possible that continuous low-dose infusions of dextran may help to stabilize the permeability barrier in patients with profound or refractory shock, reducing the need for repeated boluses, limiting the total colloid volume required. Formal clinical studies should help to assess this strategy as an alternative to conventional fluid resuscitation for severe DSS.

Dengue is a potentially serious common viral infection with no specific treatment. Plasma leakage from small blood vessels is the major severe problem, but we do not understand how this occurs. Techniques using controlled infusions of carbohydrate solutions, combined with careful measurement of the rate that the different-sized molecules clear from the circulation, have been successfully used to investigate leakage in other situations. We performed carbohydrate clearance studies in 15 Vietnamese adult males with dengue and plasma leakage, comparing results obtained during the acute illness with recovery values, and results from a group of healthy volunteers. However, we found no differences between any of the clearance profiles measured. One possible explanation may be that the carbohydrate molecules interact with blood vessels, temporarily restoring their normal barrier function. Although this means that the technique is unsuitable for investigating leakage in dengue patients, the implications for management of patients with severe leakage resulting in shock are potentially important. Patients with profound shock are usually managed with intermittent large boluses of carbohydrate or similar solutions, sometimes causing severe side-effects; however if continuous low-dose infusions actually stabilized the permeability barrier, this might reduce the need for repeated boluses, thereby minimizing these adverse effects.

Comparative disposition of pharmacologic markers for cytochrome P-450 mediated metabolism, glomerular filtration rate, and extracellular and total body fluid volume of Greyhound and Beagle dogs

The purpose of the study was to compare the disposition of pharmacologic markers for cytochrome P-450 (CYP) metabolism, glomerular filtration rate (GFR), and extracellular (ECFV) and total body fluid volumes (TBFV) of Greyhounds and Beagles. Six healthy Greyhound and six healthy Beagle dogs were studied. Antipyrine, a marker for CYP metabolism and TBFV, and inulin, a marker for the GFR and ECFV, were administered i.v. Samples were collected at predetermined times and plasma was analyzed by validated high-pressure liquid chromatography (HPLC) methods. There were no differences in the disposition or pharmacokinetic parameters for inulin between the dog breeds. However, the clearance of antipyrine (mean = 8.33 mL/min/kg) in Greyhounds was significantly slower than Beagles (13.42 mL/min/kg, P = 0.004). The volume of distribution of antipyrine was significantly larger in Greyhounds (0.789 L/kg) than in Beagles (0.644 L/kg, P = 0.01). The half-life of antipyrine was significantly longer in Greyhounds (1.09 h) compared with Beagles (0.55 h, P = 0.002). The in vitro plasma protein binding of antipyrine was significantly less in Greyhounds (28%) compared with Beagles (40.3%, P = 0.008). Greyhounds exhibited significantly slower CYP metabolism, higher TBFV, and lower in vitro protein binding of antipyrine compared with Beagles. No differences in GFR or ECFV were found.

Rapid microtiter plate assay for determination of inulin in human plasma and dialysate

A rapid, sensitive, and reproducible microtiter plate assay for the determination of inulin in human plasma, dialysate, and phosphate-buffered saline (PBS) was developed. Plasma or PBS samples (100 microl aliquots) were prepared by the addition of indole-3-acetic acid (150 microl) and HCl (3 ml) and then briefly vortex-mixed. Samples were then incubated in a 60 degrees C water bath for 20 min, cooled in a room temperature water bath for 40 min, then diluted with deionized, distilled water (DDW; 3 ml) and again vortex-mixed. Finally, an aliquot (200 microl) of each sample was transferred to a 96-well microtiter plate and read spectrophotometrically at 490 nm. Dialysate samples were processed in a similar manner, but required an initial enzymatic step in order to remove dextrose and minimize assay interference. Samples (100 microl aliquots) were prepared by the addition of glucose oxidase/catalase solution (100 microl), briefly vortex mixed, and then incubated in a 37 degrees C water bath for 60 min, samples were then reacted with indole-3-acetic acid as before. Calibration curves were linear over the concentration range of 0.5-4 mg/ml or 0.025-0.4 mg/ml for plasma or PBS and dialysate, respectively; correlation coefficients (r(2)) were >0.99. The intra- and inter-day coefficients of variation in plasma, PBS, and dialysate were <15%. This method is well suited for the rapid analysis of large numbers of samples and is currently being used for in vitro investigations of solute removal by hemodialysis.

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.

Rapid and simple determination of inulin in biological fluids by high-performance liquid chromatography with light-scattering detection

We report a new high-performance liquid chromatography method developed for measuring inulin in plasma and urine using ion moderated partition chromatography and evaporative light-scattering detection. Samples are deproteinized with a zinc acetate and phosphotungstic acid solution and added with melezitose as an internal standard. The chromatographic separation is carried out in 16 min at a flow-rate of 0.6 ml/min using deionized water as the mobile phase. Within-run precision, measured at four different concentrations (0.050 mg/ml, 0.150 mg/ml, 0.300 mg/ml and 1.200 mg/ml), ranges from 1.7 to 3.4% in plasma and from 1.5 to 3.5% in urine. Similarly, between-run precision is in plasma from 2.0 to 4.3% and in urine from 2.0 to 4.4%. Analytical recovery ranges from 97.9 to 100.1% in plasma and from 99.1 to 99.7% in urine, respectively. Detection limit (signal-to-noise ratio=3) is 5 microg/ml both in plasma and urine. The method is simple, sensitive, without interference due to hexoses or drugs commonly taken by patients with renal diseases, and offers the advantage of measuring inulin without previous hydrolysis of the molecule.

Is serum cystatin C a sensitive marker of glomerular filtration rate (GFR)? A preliminary study on renal transplant patients

Human cystatin C is a basic low molecular mass protein (13,359 Dalton) freely filtered through the glomerulus and almost completely re-absorbed and catabolized by proximal tubular cells. We measured serum cystatin C in 38 kidney transplant patients (23 males, 15 females) aged between 6 and 32 years. To assess renal function, serum and urinary creatinine were also determined in all patients, and creatinine clearance was finally calculated. Cystatin C was determined by a particle-enhanced turbidimetric assay, and creatinine was measured by gas chromatography-mass spectrometry. To compare the diagnostic efficiency of cystatin C with that of creatinine, inulin clearance was performed on 12 renal transplant patients, and receiver operating characteristic (ROC) analysis was applied. The results of this study demonstrate that serum cystatin C significantly increases in renal transplant patients with reduced creatinine clearance (< 70 mL/min per 1.73 m2) and that the diagnostic accuracy of serum cystatin C is better than of serum creatinine. Cystatin C may be utilized as a very marker of reduced GFR.