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.

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.

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.

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.

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.

Contrast media for CT. An analysis of the early pharmacokinetics.

Iohexol and meglumine-sodium diatrizoate were injected intravenously into 18 pigs as either a 99:1 or 1:99 mixture. Blood samples were taken for 30 minutes and the concentration of each of the two contrast media was measured by means of a double labeling technique with 125I and 131I. Relative concentrations of iohexol were significantly higher during the first 3 minutes when it was injected as a moderately hyperosmolar (99% iohexol) solution than when it was injected as a very hyperosomolar (99% diatrizoate) solution. The greater intravascular dilution of the 99% diatrizoate solution by extravascular water may explain this finding as well as the significantly longer rapid disposition phase and the slightly lower distribution volume of iohexol.

Biliary excretion of iodipamide and iodoxamate in normal and common bile duct-obstructed dogs.

Iodipamide and iodoxamate were compared at equimolar clinical dosages in dogs with normal, incompletely obstructed and completely obstructed common bile ducts. Forty-eight experiments were performed under general anesthesia in six cholecystomized chronic bile fistula dogs. The peak biliary iodoxamate excretion rate, but not the peak bile iodoxamate concentration, was significantly higher with normal and incompletely obstructed common bile ducts. In complete obstruction, both a significantly higher total biliary iodoxamate excretion and concentration were obtained, but this was still insufficient for radiographic opacification by conventional technique. Lesser toxicity of iodoxamate is suggested by its significantly lower serum levels, its higher bile: urine excretion ratio and its faster compensatory urinary excretion in complete common bile duct obstruction. Iodoxamate appears on this evidence to be a better cholangiographic contrast agent than iodipamide.

Human pharmacokinetics of iohexol. A new nonionic contrast medium.

The pharmacokinetics of iohexol, a new nonionic, water-soluble contrast medium, have been determined after intravenous injection in 20 healthy volunteers, at four different dose levels (125-500 mg I/kg). The apparent volume of distribution was 0.27 1/kg, indicating distribution in the extracellular water. The biologic half-life was 121 minutes, comparable with that of other intravascular contrast media. Iohexol was excreted completely unmetabolized in the urine, with a 100% recovery 24 hours after injection. A comparison of iohexol and chromium-51 (51Cr)-EDTA clearances indicates that iohexol is mainly excreted by glomerular filtration. The 51Cr-EDTA clearance was the same when injected separately and concomitantly with iohexol, indicating that glomerular filtration rate is not affected by iohexol. No dose dependency was observed in the investigated parameters t1/2 alpha, t1/2 beta, Vd, ClT or ClR. Iohexol pharmacokinetics are in correspondence with previously reported data on intravascular contrast media.

Contrast enhancement pharmacokinetics of six ionic and nonionic contrast media.

The contrast enhancement of six contrast media (CM) was compared in 13 tissues of the rat after rapid intravenous bolus injection. The rats were sacrificed at 0 and 40 seconds and 2, 5, and 15 minutes after contrast injection. 125I labeled diatrizoate, metrizamide, ioxaglate, iohexol, iopamidol, and a nonionic dimer, iodecol, were each injected at a dose of 612 mg iodine per kg body weight, and iodine concentration (IC) and contrast enhancement were calculated from radioactivity measurements. Higher blood IC values were obtained with the nonionic CM; similar enhancement patterns were seen in the spleen, heart, lungs, and brain. Renal IC was directly related to the number of iodine atoms per ion or molecule of CM. In consequence, renal IC was inversely related to the CM osmolality, but no such correlation was seen with the blood IC. Metrizamide produced the greatest IC in the organs of the gastrointestinal tract. There was no apparent correlation of IC with molecular structure of physicochemical parameters of the CM in any of the other tissues studied.

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.

Pharmacokinetics of iodoxamic acid in rhesus monkey: biliary excretion, plasma protein binding, and enterophepatic circulation.

The previously reported steady-state method allowed estimation of the capacity-limited pharmacokinetics of the cholangiographic agent, iodipamide. To circumvent the long time period required to establish each steady-state level, a dynamic method was applied to the study of the rate processes involved in the hepatic uptake and biliary excretion of a new cholangiographic agent, iodoxamic acid, in rhesus monkeys. The dynamic method has the advantage that the pharmacokinetic parameters involved in capacity-limited hepatic uptake or biliary excretion can be obtained from a single infusion experiment. The V max was 1.03 +/- 0.25 mumoles/kg/min (mean +/- SD); Km varied from animal to animal and ranged from 1.5 to 16.4 micrometer. Protein binding was estimated using equilibrium dialysis. The Freundlich isotherm yielded a linear plot when the natural logarithm of unbound iodoxamic acid concentration in plasma was plotted against the natural logarithm of its blood concentration. The plasma protein binding data also could be fitted to the Langmuir isotherm, presuming two independent classes of binding.

Use of iohexol in the radiographic diagnosis of ischemic bowel.

This study evaluates the use of iohexol as a radiographic diagnostic contrast agent in normal animals and those with experimental bowel ischemia and obstruction. Eighteen rats and 12 rabbits were gavaged with iohexol in a dose of 7.5 mL/kg using concentrations of 140 mg I/mL (isotonic with blood) or 300 mg I/mL. In addition, four rabbits had intraperitoneal iohexol injection and three were given gastrografin gavage. Experimental groups included normal bowel controls, bowel injury induced by ischemia and alcohol contact, bowel obstruction by ligature, and intraperitoneal injection. Serial abdominal radiographs and plasma concentrations of iohexol were obtained. Iohexol remained stable throughout the gastrointestinal tract, retained its intensity, and was well visualized up to four days after administration. Bowel images were fair at concentrations of 140 mg I/mL and excellent at 300 mg I/mL. Gastrografin caused bowel distention and poor visualization related to dilution. It also precipitated in the stomach. Iohexol was rapidly absorbed from the peritoneal cavity and excreted by the kidneys, without causing peritonitis. Rat plasma iohexol levels were three times controls in obstructed bowel and 80 times controls if there was mucosal injury without perforation. Rabbit peak plasma levels were 30 times greater following intraperitoneal injection than with gastric gavage. These observations suggest that iohexol may be useful as a gastrointestinal contrast agent. Measuring plasma iohexol levels may be helpful in the evaluation of suspected bowel ischemia or perforation in the clinical setting.

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.

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.

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.

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.

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.

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.

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.