An improved fluorometric method for measurement of alloxan in biological fluids

Determination of alloxan by fluorometric high-performance liquid chromatography

A fluorometric, reversed-phase high-performance liquid chromatography (RP-HPLC) method that allows quantitation of low levels of alloxan has been described. The method involved derivatization of alloxan with 500-200,000-fold excess of 1, 2-phenylenediamine (PD) in 0.1 M acetate buffer, pH 4.5 for 15 min at room temperature. The fluorescent product alloxazine (excitation: 382 nm; emission: 435 nm) was then analyzed by RP-HPLC using an Eclipse XDB-C18 (4.6 x 150 mm) column and a mobile phase consisting of 0.1% trifluoroacetic acid in 15/85 (v/v) acetonitrile/water at a flow of 1 mL/min (injection volume: 20 microL). The method is robust, and as low as 0.1 pmol of the analyte could be successfully detected and quantified. Following a minimal pre-treatment such as ultrafiltration (molecular weight cut-off 5000 Da) or protein precipitation using perchloric acid, acetonitrile, or phosphotungstic acid, the method is suitable for analysis of alloxan in complex physiological fluids (e.g. fetal bovine serum) and tissue homogenates (e.g. heart and kidney). The method has been rigorously evaluated and adapted in the laboratory for routine analysis and determination of alloxan added to cell cultures.

A method for quantitative wet chemical analysis of urinary calculi

We describe a simple method for quantitative chemical analysis of urinary calculi requiring no specialized equipment. Pulverized calculi are dried over silica gel at room temperature and dissolved in nitric acid, which was the only effective agent for complete dissolution. Calcium, magnesium, ammonium, and phosphate are then determined by conventional methods. Oxalate is determined by a method based on the quenching action of oxalate on the fluorescence of a zirconium-flavonol complex. Uric acid, when treated with nitric acid, is stoichiometrically converted to alloxan, which is determined fluorimetrically with 1,2-phenylenediamine. Similarly, cystine is oxidized by nitric acid to sulfate, which is determined turbidimetrically as barium sulfate. Protein is determined spectrophotometrically as xanthoprotein. The total mass recovery of authentic calculi was 92.2 +/- 6.7 (SD) per cent. The method permits analysis of calculi as small as 1.0 mg. Internal quality control is performed with specially designed control samples.

The effect of alloxan, and alloxan-induced diabetes on the kidney

Alloxan is known to induce diabetic renal changes as well as causing nephrotoxic alterations. However, no ultrastructural study has been performed to differentiate diabetic verses toxic affects of alloxan to the tubule and/or glomerulus. Therefore the present study used the "protected" kidney model to prevent one kidney from being exposed to the alloxan while allowing the other to receive the drug immediately. In all experimental animals the right renal hilum was gently occluded for 5 minutes and then released. This was performed prior to the injection of alloxan. Subsequently, the left renal hilum was occluded at the time of, and for 5 minutes after, alloxan administration (40 mg/kg i.v.). The experimental rats were divided into three groups: untreated diabetics, diabetics treated with protamine-zinc-insulin, and alloxan-treated rats that failed to become diabetic. Three groups of controls were included: one group received an equal volume of saline diluent as the experimental rats but no clamping of either renal hilum; another group received the saline and had the left renal hilum occluded for 5 minutes; and a third group had both the right and left renal hila occluded. All animals were followed and sacrificed after 9 weeks. Endogenous creatinine clearance did not change among groups. Alloxan-treated nondiabetic rats displayed marked interstitial nephritis in unprotected kidneys, while protected kidneys were normal. The diabetic state resulted in mesangial proliferation and focal glomerular basement membrane thickening as well as glomerular capillary endothelial abnormalities and visceral epithelial foot-process fusion. The endothelial changes consisted of focal areas showing a reduction in the size of endothelial fenestrae. All glomerular changes were ameliorated by insulin treatment. We conclude: 1) alloxan per se is distinctly nephrotoxic; and 2) the glomerular endothelium and epithelium are involved early in the course of experimental diabetes.

Blood pressure of alloxan diabetic rats at regular and high salt intake

To identify any relationship between diabetes mellitus and high salt intake in the production of hypertension, we studied the effect of a regular and high salt diet on blood pressure in rats made diabetic with alloxan. The diabetic animals developed marked hyperglycemia, glycosuria, and azotemia out of proportion to changes in glomerular filtration rate. Non-diabetic rats and diabetic rats on a high salt intake in excess of 14 mEq/day developed modest but significant increases in blood pressure, while diabetic rats on a regular diet did not. We conclude that diabetic rats have no greater susceptibility to salt-induced hypertension than rats receiving only salt. Although it is possible that dehydration may have served to attenuate blood pressure increases in our diabetic animals, the diabetic state per se does not appear to result in severe hypertension in the rat regardless of sodium intake.