A method for estimating the glomerular filtration rate in conscious monkeys.

To establish a method for estimating the glomerular filtration rate (GFR) in conscious monkeys, the radiographic contrast medium iodixanol and the standard agent inulin were coadministered as tracers to male cynomolgus monkeys (Macaca fascicularis) as a bolus injection; blood was collected after 60, 90 and 120 min. An equation based on a single-blood-sample method derived from Jacobsson's formula was prepared using the data from healthy and saline- and gentamicin-treated monkeys by a multisample strategy with iodixanol. The GFR using the equation with iodixanol was in agreement with that from the multisample method with inulin or iodixanol. When the GFR decreased to more than 60% of the basal reference level, serum creatinine concentrations tended to increase, whereas serum blood urea nitrogen concentrations fluctuated. The results suggest that the single-sample-blood method with iodixanol is a practical tool for estimating the monkey GFR in a toxicological research setting therefore minimizing animal sufferings.

Relationship of glomerular filtration rate based on serum iodixanol clearance to IRIS staging in cats with chronic kidney disease.

We examined the correlation between the glomerular filtration rate (GFR) estimated from an equation based on the serum iodixanol clearance technique and International Renal Interest Society (IRIS) stages of chronic kidney disease (CKD) in cats. The equation included the injection dose, sampling time, serum concentration and estimated volume of distribution (Vd) of the isotonic, nonionic, contrast medium iodixanol as a test tracer. The percent changes in the median basal GFR values calculated from the equation in CKD cats resembled those of IRIS stages 1-3. These data validate the association between the GFR derived from the simplified equation and IRIS stages based on the serum creatinine concentration in cats with CKD. They describe the GFR ranges determined using single-sample iodixanol clearance for healthy cats and cats with various IRIS stages of CKD.

Distribution of actin of the human erythrocyte membrane cytoskeleton after interaction with radiographic contrast media.

A type-dependent chemotoxic effect of radiographic contrast media on erythrocytes and endothelial cells was reported several times. While mechanisms of toxicity are still unclear the cellular reactions e.g. echinocyte formation in erythrocytes and the buckling of endothelial cells coincided with deterioration of capillary perfusion (in patients with coronary artery disease) and tissue oxygen tension (in the myocardium of pigs). Whether the shape changes in erythrocytes coincide with changes in the arrangement of actin, the core of the actin-spectrin cytoskeletal network and possible actor in membrane stresses and deformation is not known until now. To get specific informations actin was stained using two different staining methods (antibodies to ß-actin staining oligomeric G-actin and polymeric F-actin and Phalloidin-Rhodamin staining polymeric F-actin only). In addition, an advanced version of confocal laser scanning microscopes was used enabling the display of the actin arrangement near substrate surfaces. Blood smears were produced after erythrocyte suspension in autologous plasma or in two different plasma/RCM mixtures. In this study an even homogenous distribution of fine grained globular actin in the normal human erythrocyte could be demonstrated. After suspension of erythrocytes in a plasma/Iodixanol mixture an increased number of membrane protrusions appeared densely filled with intensely stained actin similar to cells suspended in autologous plasma, however, there in less numbers. Suspension in Iopromide, in contrast, induced a complete reorganization of the cytoskeletal actin: the fine grained globular actin distribution disappeared and only few, long and thick actin filaments bundled and possibly polymerized appeared, instead, shown here for the first time.

Technical note: Use of a simplified equation for estimating glomerular filtration rate in beef cattle.

This study was performed to clarify whether a formula (Holstein equation) based on a single blood sample and the isotonic, nonionic, iodine contrast medium iodixanol in Holstein dairy cows can apply to the estimation of glomerular filtration rate (GFR) for beef cattle. To verify the application of iodixanol in beef cattle, instead of the standard tracer inulin, both agents were coadministered as a bolus intravenous injection to identical animals at doses of 10 mg of I/kg of BW and 30 mg/kg. Blood was collected 30, 60, 90, and 120 min after the injection, and the GFR was determined by the conventional multisample strategies. The GFR values from iodixanol were well consistent with those from inulin, and no effects of BW, age, or parity on GFR estimates were noted. However, the GFR in cattle weighing less than 300 kg, aged<1 yr old, largely fluctuated, presumably due to the rapid ruminal growth and dynamic changes in renal function at young adult ages. Using clinically healthy cattle and those with renal failure, the GFR values estimated from the Holstein equation were in good agreement with those by the multisample method using iodixanol (r=0.89, P=0.01). The results indicate that the simplified Holstein equation using iodixanol can be used for estimating the GFR of beef cattle in the same dose regimen as Holstein dairy cows, and provides a practical and ethical alternative.

Glomerular filtration rate in Holstein dairy cows estimated from a single blood sample using iodixanol.

The isotonic, nonionic, contrast medium iodixanol, as a test substance, was compared with the conventional glomerular filtration rate (GFR) tracer inulin to establish a simplified procedure for estimating the GFR in Holstein dairy cows. First, inulin and iodixanol were coadministered as a bolus intravenous injection to clinically healthy cows at 30 mg/kg and 10mg of I/kg of body weight, respectively, followed by blood collection for multisample strategies. Serum iodixanol and inulin concentrations were separately determined by using HPLC and colorimetry, respectively, and blood urea nitrogen and creatinine concentrations in sera were measured. In the multisample method, the GFR values estimated by iodixanol were consistent with those estimated by inulin. No effects of body weight, age, or parity on GFR estimates were noted with either protocol used. No difference was observed between the GFR values obtained from nonlactating and lactating cows, suggesting that no transfer of iodixanol to milk occurred. An equation for calculating the GFR in the single-sample method was derived from the injected dose, sampling time, serum concentration, and estimated volume of distribution based on data from the multisample method in clinically healthy cows and cows with reduced renal function. The GFR values estimated by the single-sample method were in good agreement with those calculated by using the multisample method. These results demonstrate that the single-sample method using iodixanol can be applied as an alternative procedure for screening GFR in dairy cows.

Estimation of glomerular filtration rate in rabbits by a single-sample method using iodixanol.

To estimate the glomerular filtration rate (GFR) in conscious rabbits, a single-sample method using the non-ionic contrast medium iodixanol was compared with a three-sample method using the standard agent inulin. Iodixanol and inulin were co-administered intravenously to male New Zealand White rabbits at 60 mg I/kg and 40 mg/kg, respectively, and blood was collected 30, 60, 90 and 120 min later. Serum iodixanol and inulin concentrations were separately determined by high performance liquid chromatography and colorimetry, respectively. Serum urea nitrogen (UN) and creatinine concentrations were also determined. Based on the data from healthy and cisplatin-treated rabbits, the GFR estimated by iodixanol was well consistent with that by inulin. Further, when the GFR decreased to more than 60% of the reference value, serum creatinine concentrations became elevated. However, serum UN concentrations exhibited wide fluctuations, presumably due to a difference in renal handlings. The single-sample method using iodixanol was considered to be an expedient tool in both clinical and research settings, because the stress due to a multi-sample method was reduced.

Simplified procedure for the estimation of glomerular filtration rate following intravenous administration of iodixanol in cats.

OBJECTIVE: To compare the use of a single-sample method involving IV administration of iodixanol with a multisample method involving inulin for the estimation of glomerular filtration rate (GFR) in cats. ANIMALS: 24 cats, including 15 healthy cats and 9 cats with naturally occurring renal diseases. PROCEDURES: Each cat was coadministered iodixanol (a nonionic contrast medium; dose providing 40 mg of I/kg) and inulin (50 mg/kg), IV, and blood samples were collected 60, 90, and 120 minutes later. Serum iodixanol and inulin concentrations were determined by means of high-performance liquid chromatography and colorimetry, respectively. Serum urea nitrogen and creatinine concentrations were also measured. RESULTS: Analysis of the data from healthy cats and cats with naturally occurring renal diseases revealed an excellent correlation between GFR values estimated by the multisample and single-sample methods with iodixanol. Likewise, GFR values estimated from the single-sample method with iodixanol were closely correlated with those calculated from the multisample method with inulin. CONCLUSIONS AND CLINICAL RELEVANCE: For estimation of GFR in cats, use of a single-sample method with iodixanol, instead of a multisample procedure, may be an expedient tool in both clinical and research settings because of its benefits to patient well-being as a result of reduced stress associated with blood sample collection.

Colorimetric assay for the quantification of serum iodixanol concentration and its application on estimation of glomerular filtration rate in cattle.

A colorimetric assay used to quantify the non-ionic contrast medium iodixanol in sera was validated and compared with high-performance liquid chromatography. The application of this assay to estimate glomerular filtration rates (GFR) in cattle was examined. Serum iodixanol was de-iodinated by alkaline hydrolysis and the amount of released iodine was subsequently determined using a ceric arsenite method. There was a close correlation between the two methods using identical specimens. In clinically healthy cattle with different body weights, the reference value (166.3-178.8 mL/min/m(2)) based on body surface area was fairly stable as compared with that (2.13-3.63 mL/min/kg) based on body weight. Based on GFR data in healthy and renal-impaired cattle, when the GFR decreased to more than 60% of the reference value, serum urea nitrogen and creatinine concentrations increased. The colorimetric assay is a simple method for the estimation of GFR in cattle and requires no expensive equipment.

Estimation of glomerular filtration rate in calves using the contrast medium iodixanol.

To develop a simple procedure for estimating glomerular filtration rate (GFR) in calves, a three-sample method using iodixanol was first compared to that using the standard agent inulin. Iodixanol and inulin were co-administered intravenously to calves at 40 mg I/kg and 40 mg/kg, respectively, and blood was collected 30, 60, 120, and 180 min later. Serum iodixanol and inulin concentrations were separately determined by high performance liquid chromatography and colorimetry. Serum urea nitrogen (UN) and creatinine concentrations were also measured. GFR estimated by iodixanol was consistent with that using inulin in clinically healthy calves. Based on GFR estimations in healthy calves and those renal-loaded with iodixanol, it was found that the serum creatinine concentrations became elevated when GFR decreased to 60% of the reference value. In contrast, serum UN concentrations fluctuated widely, presumably due to extra-renal factors. When GFR was estimated using the three-sample method and compared with the single-blood-sample method, 62/69 (90%) of samples tested were within the agreement plots. The results demonstrated that the single-blood-sample method using iodixanol may be useful in monitoring GFR in calves.

Serum clearance of iodixanol for estimating glomerular filtration rate in calves.

To evaluate serum clearance of iodixanol, applicable to the estimation of glomerular filtration rate (GFR), clinically healthy and experimentally-induced nephropathy calves were prepared. Iodixanol was administered intravenously at 40 mg I/kg, and blood was withdrawn 60, 120, and 180 min later. Serum iodixanol concentration was determined by high-performance liquid chromatography. No statistical difference in GFR was noted between strains (Holstein vs. Japanese Black) or sexes, and the α(2)-adrenergic agonist xylazine increased GFR. In calves subjected to right renal vessel ligation, followed by a left nephrectomy, a marked reduction in GFR was observed with renal ischemic changes. These results suggest that the GFR estimation by serum iodixanol clearance is a ready-to-use tool in calf research and practice owing to the ease of monitoring serial renal function.

Optimum conditions for serum clearance of iodixanol, applicable to the estimation of glomerular filtration rate in horses.

To estimate the glomerular filtration rate (GFR) in horses, an optimum dose of the nonionic contrast medium iodixanol as a tracer was assessed with blood-sample times. Iodixanol was administered intravenously at 10-40 mg I/kg to geldings and mares, and blood was collected 30, 60, 90, 120, 150, and 180 min later. Serum iodixanol concentration was determined by high-performance liquid chromatography (HPLC), and serum urea nitrogen (UN) and creatinine concentrations were also measured. The combination of 20 mg I/kg iodixanol and sampling times of 60, 90, and 120 min after injection was considered to be appropriate for practical use. In clinically healthy horses, the reference values were determined to be 1.90 ± 0.03 ml/min/kg (150.8 ± 2.94 ml/min/m2), consistent with historical data using different tracers. The result suggests that serum clearance of iodixanol is a ready-to-use tool for a screening of alterations in the equine GFR, although it is necessary to perform a more longitudinal study using horses with a variety of renal functions.

Sequential measurements of glomerular filtration rate in conscious rats by a bolus injection of iodixanol and a single blood sample.

To estimate the glomerular filtration rate (GFR) sequentially in conscious rats, we validated a single-blood-sample method using a bolus injection of the nonionic contrast medium iodixanol as a tracer. First, to clarify basal age-related GFR profiles, iodixanol was intravenously administered once weekly at 1500 mg kg(-1) I to clinically healthy male F344 rats from 6 to 15 weeks of age. The blood sample was collected 120 min later, and serum iodixanol concentration was measured by HPLC. GFR values decreased gradually by 9 weeks, presumably due to rapidly increased body weights, and then remained constant from 10 weeks onward. When converting the GFR from body weight to body surface area, the reference range (40-60 ml min(-1) m(-2) ) in the latter was much more stable than that (6-11 ml min(-1) kg(-1) ) in the former. For nephropathy rats induced by cisplatin (3.75-7.5 mg kg(-1) , i.v., single dose), bromoethylamine hydrobromide (BEA, 250-500 mg kg(-1) , i.v., single dose) or puromycin aminonucleoside (PAN, 15 mg kg(-1) day(-1) , s.c., 10 days), GFR decreased or tended to decrease before increasing in serum urea nitrogen (UN) and creatinine concentrations. Accordingly, serum UN and creatinine concentrations became elevated when the GFR decreased to 50-60% of the basal value. This method without urine collection contributes to the reduction of animal numbers because of repeated application to the same animals.

Calculation of glomerular filtration rate in conscious rats by the use of a bolus injection of iodixanol and a single blood sample.

INTRODUCTION: To establish a simple and convenient procedure for the determination of glomerular filtration rate (GFR) in conscious rats, we developed a single-blood-sample method, in contrast to the conventional three-sample method, using a bolus injection of the nonionic contrast medium iodixanol. METHODS: Iodixanol was intravenously administered at 1500 mg I/kg to healthy or renal-impaired rats, and blood was collected 60, 120, and 180 min later. Serum iodixanol concentrations were measured by HPLC, and serum urea nitrogen (UN) and creatinine concentrations were determined as renal function tests. RESULTS: In rats subjected to 1/2 and 3/4 nephrectomies, GFR values decreased significantly without and with increases in serum UN and creatinine concentrations, respectively. In rats treated subcutaneously with gentamicin sulfate (GM) at 80 mg/kg/day or puromycin aminonucleoside (PAN) at 15 mg/kg/day for 10 consecutive days, the GFR values decreased or showed a tendency to decrease before increases in serum UN and creatinine concentrations. Accordingly, when the GFR decreased to more than 60% of the basal value, serum UN or creatinine concentrations became elevated. The GFR values obtained from the three-sample method were closely correlated (r=0.83) with those calculated from the estimated distribution volume (V) and serum iodixanol concentration 120 min after iodixanol injection in the single-blood-sample method in which serum iodixanol concentrations ranged between 20 and 250 microg I/mL. DISCUSSION: These results suggest that the single-blood-sample method with a bolus injection of iodixanol, allowing for the repeated use of the same animals, is an expedient procedure without ensuring accurate urine collection.

Development and validation of an HPLC-UV method for iodixanol quantification in human plasma.

Iodixanol is a widely used iso-osmolar contrast medium agent. Similar to iohexol, it can also be a good exogenous marker for the measurement of glomerular filtration rate (GFR). This article describes the development and validation of an HPLC-UV method for quantification of iodixanol in human plasma. Internal standard, iohexol (20 microl, 1 mg/ml), and perchloric acid (30 microl, 20%, v/v) were added to plasma samples (300 microl), followed by neutralization with 10 microl potassium carbonate (5M). Samples were centrifuged and 10 microl of the supernatant was injected onto a C(18) EPS analytical column (3 microm particle size, 150 mm x 4.6 mm). The extraction method yielded >95% recovery for both iodixanol and iohexol. The mobile phase consisted of 0.1% (w/v) sodium formate buffer and acetonitrile. Iohexol and iodixanol peaks were eluted at approximately 5 and 9 min, respectively using a fast gradient method. The assay lower limit of detection was 2.0 microg/ml and lower limit of quantification was 10 microg/ml. The calibration curves, assessed in six replicates, were linear over an iodixanol concentration range of 10-750 microg/ml. Intra- and inter-day accuracy was >95% and precision expressed as % coefficient of variation was <10%. This method is simple, accurate, precise and robust and can potentially be used for iodixanol quantification in large-scale clinical studies.

Iso-osmolar radio contrast iodixanol in patients with chronic kidney disease.

BACKGROUND: Although radio contrast volume has been associated with worsening post-procedural kidney function, this relationship has not been extensively studied using an iso-osmolar contrast agent in chronic kidney disease patients. METHODS: We retrospectively studied patients undergoing cardiac catheterization at the University of Minnesota from 2000 to 2004, using the iso-osmolar contrast agent, iodixanol. All patients were included who had calculated creatinine clearance (CCR) < 60 mL/min, not on dialysis, and serum creatinine measured on the same day and within 7 days after the procedure. Comparison of a subgroup with severe chronic kidney disease and diabetes mellitus was compared to a similar historical control group that used the low-osmolar contrast agent, iohexol. RESULTS: Serum creatinine and CCR were 2.9 +/- 1.5 mg/dL and 33.4 +/- 12.0 mL/min (mean +/- standard deviation), respectively, at baseline in 117 cases. Peak creatinine increased by 0.03 +/- 0.7 mg/dL after 84.3 +/- 67.3 mL of iodixanol was used. Contrast-induced nephropathy definition was fulfilled in 22 (18.8%) cases. A non-significant negative correlation was found between the volume of iodixanol and the change in creatinine (r2 = 0.0011, p = 0.7254). A subgroup with severe chronic kidney disease and diabetes mellitus with iodixanol had a significantly lower creatinine increase (n = 25, 0.09 +/- 0.5 mg/dL), compared to historical controls (n = 42, 0.7 +/- 0.8 mg/dL) with iohexol (p < 0.001). A non-significant positive correlation between volume of contrast and change in creatinine was found in this subgroup who received iodixanol (n = 25, r2 = 0.0756, p = 0.1835), but was significant in the historical controls who received iohexol (n = 42, r2 = 0.135, p = 0.017). CONCLUSIONS: The volume of iso-osmolar radio contrast does not affect the incidence of contrast-induced nephropathy in patients with chronic kidney disease. A randomized trial evaluating the incidence of contrast nephropathy would verify the safety of ad hoc versus staged angiographic procedures in this population.

On-line dialysis and quantitative high-performance liquid chromatography analysis of iodixanol in human, rat and monkey plasma.

A fully automated HPLC method for analysing the non-ionic X-ray contrast agent iodixanol in plasma samples, using on-line dialysis for sample preparation, was developed. Optimal conditions were obtained with a static dialysis donor solution of 110 microl and 4 ml of recipient solution (dialysate) pulsed onto a trace enrichment column, giving maximum 55% dialysis efficiency in less than the chromatographic run time of 20 min. Hence, one sample could be dialysed during the analysis of the previous. The maximum load of iodixanol on the trace enrichment column was 3.75 mg. Validation showed that the method was selective for iodixanol, sensitive down to 84 pmol/ml and had a high precision over a linear range up to 320 nmol/ml. Although developed for iodixanol, the method can easily be modified and applied to other substances with similar properties, i.e., substances having low protein binding and high water solubility, but strong enough stationary phase affinity to be retained by an appropriate trace enrichment column.

Safety and pharmacokinetics of iotrolan in hysterosalpingography. Retention and irritability compared with Lipiodol.

RATIONALE AND OBJECTIVES: The authors compared the safety and pharmacokinetics of Iotrolan (water-soluble) in hysterosalpingography (HSG) with those of Lipiodol (oil-soluble). METHODS: Iotrolan and Lipiodol were administered intraperitoneally at doses of 100 mg iodine/kg to female rabbits. Retention in the body was investigated by x-ray imaging, plasma kinetics, and urinary and fecal excretion. Irritability in the abdomen was investigated by histologic examination. RESULTS: Iotrolan was entirely excreted into the urine within 2 days after administration. Conversely, Lipiodol was excreted into the urine, had a half-life of 50 days, and was retained for more than 21 days in the abdomen. Iotrolan induced no inflammatory reaction in the abdomen, whereas Lipiodol induced a marked abdominal inflammatory reaction, including granuloma formation. Iotrolan had no effect on iodine concentration in the thyroid; Lipiodol increased iodine concentration significantly. CONCLUSIONS: Iotrolan, which is a water-soluble and nonionic dimeric contrast medium, has potential greater safety for use in HSG than Lipiodol.

Image quality and safety in pediatric urography using an ionic and a non-ionic iodinated contrast agent.

The safety and diagnostic efficacy of the new non-ionic, monomeric contrast medium iopentol (Imagopaque) were evaluated and compared with those of the ionic medium metrizoate (Isopaque), in urography in children in a randomized, double-blind, parallel study. The trial comprised 59 children aged from 3 months to 8 years; children with predefined risk factors were not included. The difference in attenuation between the renal and perirenal tissue, assessed from film density measurements, was chosen as the main variable. Diagnostic efficacy was also evaluated subjectively from demarcation of the kidney and the pelvic structures. There was no statistically significant difference between the groups in the diagnostic efficacy. Serious adverse events did not occur in either group. Mild to moderate, transient adverse events were significantly less frequent in the iopentol group than in the metrizoate group, but in no case was medical treatment required. There were no changes or trends toward changes of clinical importance in either group, in serum chemistry variables measured in blood samples taken 2 min after injection of contrast medium compared to baseline values.

Pharmacokinetics of iopentol in patients with chronic renal failure.

Iopentol 350 mg I/ml was injected in doses of 265 to 533 mg I/kg b.w. (mean 417 mg I/kg b.w.) in 10 patients with advanced nondiabetic chronic renal failure (S-creatinine 672 +/- 259 mumol/l (mean +/- SD)). Urine (10 patients) and feces (7 patients) were collected at 24 h intervals for 5 days after the injection. The elimination of iopentol was delayed. Five days after injection a mean of 54% (range 35-79%) of the dose was recovered in urine, and 11% (0-20%) in feces. Mean elimination half-life was 28.4 h, about 14 times the half-life found in healthy volunteers. The apparent volume of distribution was 0.27 l/kg b.w., indicating distribution only to extracellular fluid. Using renal iopentol clearance as reference value, GFR was overestimated by 40 to 60% with iopentol total clearance, showing extrarenal elimination of iopentol. The difference was most pronounced in patients with low GFR. In conclusion, this study shows an extrarenal elimination of iopentol and demonstrates a substantial increase in the fecal elimination in patients with severe renal failure.