Monitoring of the degradation kinetics of diatrizoate sodium to its cytotoxic degradant using a stability-indicating high-performance liquid chromatographic method.

The X-ray diagnostic agent sodium diatrizoate (DTA) was studied for chemical degradation. The 3,5-diamino derivative was found to be the alkaline and acidic degradation product. The 3,5-diamino degradate is also the synthetic precursor of DTA and it is proved to have cytotoxic and mutagenic effects. A sensitive, selective and precise high-performance liquid chromatographic stability-indicating method for the determination of DTA in the presence of its acidic degradation product and in pharmaceutical formulation was developed and validated. Owing to the high toxicity of the degradation product, the kinetics of the acidic degradation process was monitored by the developed RP-HPLC method. The reaction was found to follow pseudo-first order kinetics. The kinetic parameters such as rate constant (K) and half-life (t½ ) were calculated under different temperatures and acid concentrations; activation energy was estimated from the Arrhenius plot. The developed RP-HPLC method depends on isocratic elution of a mobile phase composed of methanol-water (25:75 v/v; pH adjusted with phosphoric acid), and UV detection at 238 nm. The method showed good linearity over a concentration range of 2-100 µg/mL with mean percentage recovery of 100.04 ± 1.07. The selectivity of the proposed method was tested using laboratory-prepared mixtures. The proposed method has been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives and the results were statistically compared with the official USP method. Validation of the proposed method was performed according to International Conference on Harmonization guidelines.

A comparative study between three stability indicating spectrophotometric methods for the determination of diatrizoate sodium in presence of its cytotoxic degradation product based on two-wavelength selection.

Three sensitive, selective, and precise stability indicating spectrophotometric methods for the determination of the X-ray contrast agent, diatrizoate sodium (DTA) in the presence of its acidic degradation product (highly cytotoxic 3,5-diamino metabolite) and in pharmaceutical formulation, were developed and validated. The first method is ratio difference, the second one is the bivariate method, and the third one is the dual wavelength method. The calibration curves for the three proposed methods are linear over a concentration range of 2-24 µg/mL. The selectivity of the proposed methods was tested using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of DTA in pharmaceutical dosage forms without interference from other dosage form additives. The results were statistically compared with the official US pharmacopeial method. No significant difference for either accuracy or precision was observed.

Reversal of radiocontrast medium toxicity in human renal proximal tubular cells by white grape juice extract.

Radiocontrast media (RCM)-induced nephrotoxicity (CIN) is a major clinical problem accounting for 12% of all hospital-acquired cases of acute kidney injury. The pathophysiology of CIN is not well understood, but direct toxic effects on renal cells have been postulated as contributing to CIN. We have investigated the effect of a white grape (Vitis vinifera) juice extract (WGJe) on human renal proximal tubular (HK-2) cells treated with the radiocontrast medium (RCM) sodium diatrizoate. WGJe caused an increase in phosphorylation of the prosurvival kinases Akt and ERK1/2 in HK-2 cells. Treatment of HK-2 cells with 75 mgI/ml sodium diatrizoate for 2.5h and then further incubation (for 27.5h) after removal of the RCM caused a drastic decrease in cell viability. However, pre-treatment with WGJe, prior to incubation with diatrizoate, dramatically improved cell viability. Analysis of key signaling molecules by Western blotting showed that diatrizoate caused a drastic decrease in phosphorylation of Akt (Ser473), FOXO1 (Thr24) and FOXO3a (Thr32) during the initial 2.5h incubation period, and WGJe pre-treatment caused a reversal of these effects. Further analysis by Western blotting of samples from HK-2 cells cultured for longer periods of time (for up to 27.5h after an initial 2.5h exposure to diatrizoate with or without WGJe pre-treatment) showed that WGJe pre-treatment caused a negative effect on phosphorylation of p38, NF-κB (Ser276) and pERK1/2 whilst having a positive effect on the phosphorylation of Akt, FOXO1/FOXO3a and maintained levels of Pim-1 kinase. WGJe may alleviate RCM toxicity through modulation of signaling molecules that are known to be involved in cell death and cell survival and its possible beneficial effects should be further investigated.

Protective effect of adrenomedullin on contrast induced nephropathy in rats.

BACKGROUND AND AIMS: Contrast-induced nephropathy (CIN) has a growing incidence in which renal vasoconstriction and medullary hypoxia are important mechanisms. Therapeutic approaches are very restricted and there is a considerable interest in advancing preventive strategies. Adrenomedullin is a relatively novel peptide having antioxidant, vasoactive and vasodilatory properties. We aimed to investigate whether adrenomedullin might have a preventive role against the development of experimental CIN. METHODS: Wistar albino rats (n=24) were allocated randomly into four equal groups of 6 each; Control (C), Adrenomedullin (A), Contrast Media (CM) and Adrenomedullin plus Contrast Media (ACM). All rats were deprived of water from day 1 to day 4 during 72 hours. Then, intravenous administrations of chemicals were performed. Adrenomedullin was given at dose of 12µg/kg to groups A and ACM. A single dose of high-osmolar contrast media; diatrizoate (Urografin 76%, Schering AG, Germany) was injected to groups CM and ACM at dose of 10mL/kg. On day 1 and 6 blood samples were drawn for renal function tests and inflammatory markers including TNF-α IL-1β, IL-6 and IL-18. After sacrification, kidney histologies were examined with hematoxylin-eosin staining. RESULTS: Compared to CM group, serum cystatin-C levels on 6th day were found significantly lower in ACM group (p<0.05). Additionally, daily protein excretion rates, absolute changes in daily urine output and creatinine clearance values were significantly lower in ACM group than those in CM group (p<0.05). In histopathological evaluation, regarding the degree of tubular damage and medullary congestion scores, ACM group had slightly better scores compared to CM group; however the differences did not reach significance as shown in inflammatory markers. CONCLUSION: This study demonstrated a beneficial impact of adrenomedullin on deteriorated renal function tests in an experimental CIN model. Adrenomedullin might be a candidate agent for prophylaxis of CIN. However, further studies are needed to shed more light on this issue.

Effects of intrathecal injection of diatrizoate on dopamine receptors.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether adverse reactions similar to those that occur in patients receiving antipsychotic medication may occur after inadvertent intrathecal injections of some contrast material. MATERIALS AND METHODS: Recombinant human dopamine-2 (D-2) receptors were incubated together with tritiated (hydrogen 3) spiperone, a D-2 receptor agonist commonly used in binding studies, and three types of contrast material (sodium/meglumine diatrizoate; meglumine iothalamate; and iohexol) in different concentrations to determine competitive binding potentials. Nonspecific binding was also assessed. Membranes were washed, filtered, and counted in a scintillation counter. RESULTS: At several different concentrations, diatrizoate demonstrated a potential to displace the binding of spiperone to the D-2 receptors, whereas the other two contrast materials tested (iothalamate meglumine and iohexol) showed only weak binding potentials. CONCLUSION: Diatrizoate, which has been incriminated in most adverse reactions resulting from the inadvertent intrathecal injection of a contrast material, may produce symptoms similar to those of the neuroleptic malignant syndrome by blocking neurotransmission through dopamine receptors. Although antipsychotic drugs produce this parkinsonism-like effect only after prolonged use, it is probable that diatrizoate produces the effect immediately by virtue of the high concentrations that may accumulate at the base of the brain after myelography. Also worthy of note is the fact that the two other contrast materials that have produced a number of reported adverse reactions share a molecular similarity to diatrizoate that is not found with other contrast materials.

Role of NO in endothelin-regulated drug transport in the renal proximal tubule.

We previously demonstrated in intact killifish renal proximal tubules that endothelin (ET), acting through an ET(B) receptor and protein kinase C (PKC), reduced transport mediated by multidrug resistance-associated protein 2 (Mrp2), i.e., luminal accumulation of fluorescein methotrexate (FL-MTX) (Masereeuw R, Terlouw SA, Van Aubel RAMH, Russel FGM, and Miller DS. Mol Pharmacol 57: 59-67, 2000). In the present study, we used confocal microscopy and quantitative image analysis to measure Mrp2-mediated transport of FL-MTX in killifish tubules as an indicator of the status of this ET-fired, intracellular signaling pathway. Exposing tubules to sodium nitroprusside (SNP), a nitric oxide (NO) donor, signaled a reduction in luminal accumulation of FL-MTX, which suggested pathway activation. N(G)-monomethyl-L-arginine (L-NMMA), an NO synthase inhibitor, blocked the action of ET-1 on transport. Because SNP effects on transport were blocked by bisindoylmaleide, a PKC-selective inhibitor, but not by RES-701-1, an ET(B)-receptor antagonist, generation of NO occurred after ET(B) receptor signaling but before PKC activation. NO generation was implicated in the actions of several nephrotoxicants, i.e., diatrizoate, gentamicin, amikacin, HgCl(2), and CdCl(2), each of which decreased Mrp2-mediated transport by activating ET signaling. For each nephrotoxicant, decreased FL-MTX transport was prevented when tubules were exposed to L-NMMA. ET-1 and each nephrotoxicant stimulated NO production by the tubules, as determined by a fluorescence-based assay. Together, the data show that NO generation follows ET binding to the basolateral ET(B) receptor and that, in activating the ET-signaling pathway, nephrotoxicants produce NO, a molecule that could contribute to subsequent toxic effects.

Differential effects of radiocontrast agents on human umbilical vein endothelial cells: cytotoxicity and modulators of thrombogenicity.

UNLABELLED: The endothelium plays a central role in the regulation of blood flow and coagulation. The impact of radiocontrast agents on endothelial cells is therefore potentially clinically important, particularly in percutaneous interventions for acute coronary thrombosis. The effects of radiocontrast agents on endothelial cell viability and determinants of thrombogenicity were studied in human umbilical vein endothelial cells (HUVECs) in vitro. Intercellular tight junctions were assessed using immunofluorescence microscopy and measurement of the transmonolayer electrical resistance (TMR). The concentrations of endothelin-1 (E), von Willebrand factor (vWF), plasminogen activator inhibitor-1 (PAI-1) and thrombomodulin (T) were measured in the cell culture media. The ionic, high osmolal radiocontrast agent diatrizoate induced concentration-dependent cell death and an opening of tight junctions with the attendant abolition of the TMR. The concentration of E decreased, vWF increased in the cell culture media, the concentration of PAI-1 and T was not significantly changed by diatrizoate. Radiocontrast agents with reduced osmolality (ioxaglate: ionic; iopamidol: non-ionic) induced an increase in PAI-1 and vWF, but E and T were not significantly changed. CONCLUSIONS: Radiocontrast agents have differential effects on endothelial cells in vitro including the secretion of modulators of thrombogenesis. The effects are most pronounced in the markedly hyperosmolal compound diatrizoate suggesting a contributory role of hypertonicity. Ioxaglate and iopamidol both increased the prothrombotic factors vWF and PAI-1 to the same degree indicating a similar risk of thrombogenicity between low-osmolal ionic and non-ionic radiocontrast agents in this in vitro model.

Glucose alters the susceptibility of mesangial cells to contrast media.

RATIONALE AND OBJECTIVES: Diabetic patients frequently suffer contrast media-induced nephropathy. Hyperglycemia in diabetes mellitus causes gradual deterioration of glomerular mesangial cells (MCs) in the kidney. In this study, the authors investigated the response of rat MCs cultured in high-glucose medium to diatrizoate and iohexol, high- and low-osmolar contrast media, respectively. METHODS: Isolated rat MCs were precultured under basal-glucose (5.5 mmol/L) and high-glucose (30 and 55 mmol/L) conditions for 24 hours to mimic hyperglycemia in diabetes mellitus and then were exposed to diatrizoate (40 and 80 mg I/mL) and iohexol (80, 120, 160 mg I/mL) for 2 hours. The cytotoxic effects of diatrizoate and iohexol were monitored by neutral red uptake in MCs. The protective effects of an antioxidant, d-alpha-tocopherol (Toc), on cytotoxicity of the contrast media were determined when MCs were precultured with Toc under high-glucose conditions or were exposed to the contrast media together with Toc. Peroxide levels in the cells exposed to the contrast media were analyzed by flow cytometry using dichlorofluorescin diacetate. RESULTS: Exposure to both contrast media (diatrizoate and iohexol) induced a concentration-dependent decrease in viability of the cells precultured under basal-glucose conditions (5.5 mmol/L). Preculture under high-glucose conditions (30 and 55 mmol/L) augmented the cytotoxic effects of both contrast media. An increase in the intracellular peroxide level was detected after exposure to both contrast media. Preculture with Toc prevented augmentation of the cytotoxic effects of diatrizoate by the higher glucose concentration (55 mmol/L). The exposure to diatrizoate together with Toc also attenuated its cytotoxic effects. Toc showed no such protective effects against iohexol exposure. CONCLUSIONS: These findings suggest that high-glucose conditions enhance the susceptibility of MCs to the cytotoxic effects of both contrast media; the enhanced susceptibility was in part attributable to oxidative stress caused by high-glucose conditions; diatrizoate exerted the cytotoxic effects by means of oxidative stress; and iohexol appeared to exert its cytotoxicity in a manner different from diatrizoate.

Reversibility of experimental acute renal failure in rats: assessment with USPIO-enhanced MR imaging.

The purpose of this study was to evaluate the potential reversibility of kidney lesions in an experimental model of acute renal failure using ultra-small particles of iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging. This study was conducted in 21 uninephrectomized rats using a model of iodinated contrast media-induced renal failure. Thirteen rats received selective intraarterial renal administration of diatrizoate (370 mg/ml) and were compared with two control groups, including six animals injected with saline and two noninjected animals. MR imaging was performed 28 hours, 8 days, and 22 days after the procedure. Each MR session included axial and coronal T1- and coronal T2-weighted images before and after intravenous administration of 60 micromol Fe/kg of USPIO. The rats were sacrificed immediately after the last MR session for pathologic evaluation. MR images were qualitatively and quantitatively interpreted with respect to pathologic data, and differences were statistically studied. At day 22, histology showed 4 severely diseased kidneys with focal areas of necrosis, 5 mildly diseased kidneys with tubular vacuolization, and 12 normal kidneys. On quantitative data, a high correlation between the percentage of negative enhancement and histologic data was observed (P < 0.05). Qualitative interpretation showed a sensitivity and specificity of USPIO-enhanced T2-weighted MR images of 88% and 91%, respectively. Follow-up enhancement curves showed a constant increase of intrarenal USPIO negative enhancement in normal kidneys between day 1 and day 22, whereas all severely involved kidneys displayed higher USPIO negative enhancement at day 1 without significant changes over time until day 22. USPIO may be useful for in vivo follow-up of the reversibility of experimentally induced iodinated contrast media renal impairment in animals.

Effects of radiocontrast, mannitol, and endothelin on blood pressure and renal damage in the aging male spontaneously hypertensive rat.

RATIONALE AND OBJECTIVES: The purpose of this research was to study the effects of the radiocontrast medium (CM) Hypaque-76 (diatrizoate meglumine sodium), equiosmolar mannitol, and endothelin on blood pressure and renal damage in a aging male spontaneously hypertensive rat, a small animal model for CM-induced renal damage. The importance of the pressor effect and the high osmolality of CM in producing renal damage was investigated by first reducing the blood pressure with pentobarbital anesthesia, which suppresses sympathetic nervous system activity, then testing the effects of CM, saline, mannitol, and the potent vasoconstrictor endothelin alone and in combination with CM. METHODS: Systolic blood pressure was measured in 14-month-old male rats (1) when awake, (2) after pentobarbital anesthesia, (3) after the administration of saline, CM, mannitol, endothelin, or CM plus endothelin, (4) after awakening the same day, and (5) the following day while awake. Renal damage was quantified by evaluating histopathologically the left kidney removed the day after administration of test substances. RESULTS: The pentobarbital-lowered blood pressure remained depressed after saline and mannitol but rose dramatically after CM, endothelin, and CM plus endothelin. Renal damage, compared with the saline controls, occurred with CM, mannitol, endothelin, and endothelin plus CM. The order of increasing severity was mannitol = CM < endothelin < endothelin plus CM. CONCLUSIONS: The effect of CM on systolic blood pressure is not related to its osmolality. High osmolality, however, appears to be a factor in CM-induced renal damage. Ischemia and direct nephrotoxicity are factors contributing to the renal-damaging effects of CM, mannitol, and endothelin.

Biodegradation of the iodinated X-ray contrast media diatrizoate and iopromide.

The degradation of the iodinated contrast media diatrizoate and iopromide was investigated in laboratory tests. With regard to the expected behaviour of the contrast media in the environment, test systems with activated sludge, river water and river water plus sediment were established. In some of the experiments 14C-labelled contrast media were used to study degradation at low concentrations and to detect the transformation products. Degradation by as well as binding to aerobic-activated sludge of diatrizoate was poor, suggesting that this substance is hardly retained in sewage treatment plants. In systems with river water and sediment deacetylation of diatrizoate started after a lag period of 3 weeks and followed first order kinetics with rate constants of approximately 0.15 day-1. Two metabolites were formed that were stable until day 200 of aerobic incubation. Finally, further transformation of the aerobic metabolites was observed under anoxic conditions. In activated sludge, approximately 85% of iopromide were transformed into two metabolites. Like the parent compound they were highly hydrophilic and less than 16% were bound to sludge solids. In water/sediment systems, disappearance of iopromide started spontaneously with a first order constant of 0.04 day-1. One metabolite that was stable throughout the incubation period was formed with a delay of 20 days. In river water the concentration-dependent disappearance of iopromide was studied. The shortest half-life was 3.1 days at a concentration of 16.0 mumol l-1 and increased at concentrations below and above this value. The metabolites of iopromide were not identified, but partial deiodination of iopromide was shown. Mineralisation of the two contrast media or their metabolites to carbon dioxide was not observed.

Histamine release and contrast media-induced renal vasoconstriction.

RATIONALE AND OBJECTIVES: The authors' purpose was to investigate the role of histamine release causing renal vasoconstriction induced by application of contrast media, an important element in contrast medium-induced nephrotoxicity. MATERIALS AND METHODS: Isometric contractions in rabbit segmental renal arteries stimulated with KCl and increasing concentrations of the ionic contrast medium diatrizoate and the nonionic agents iomeprol and iodixanol were studied both with and without increasing concentrations of the histamine H1 and H2 blockers diphenhydramine and cimetidine. Histamine concentrations after contrast medium application were determined. RESULTS: Contrast-induced, dose-dependent, reversible renal artery contractions of 27%, 4.5%, and 5% of the control KCl contraction were found for diatrizoate, iodixanol, and iomeprol respectively. Those induced by the ionic contrast medium were statistically significantly higher (P < .01). Contractions were partially inhibited by diphenhydramine (49%) but not by cimetidine. Significant elevation of histamine concentrations (P < .05) was detected only after stimulation with diatrizoate but not with nonionic agents. CONCLUSION: Ionic contrast medium induces histamine release leading to renal vasoconstriction, which can be partly blocked by H1 blockers. Histamine has no effect on renal vasospasm induced by nonionic contrast media.

Early glomerular effects of contrast media in rats: evaluation with a simple method.

The aim of this study was to evaluate the early effects of high and low-osmolar contrast media on glomerular function in rats by using a new method based on the measurement of the urinary excretion of 99mTc-DTPA. Thirty-six Sprague-Dawley male rats were examined: nine rats were injected with diatrizoate (ionic high-osmolar contrast medium), nine rats with iohexol (nonionic low-osmolar contrast medium), and nine rats with saline as controls. The urinary excretion of 99mTc-DTPA in the first minutes after i.v. injection was assumed as an index of glomerular filtration rate. A lower urinary excretion of 99mTc-DTPA was found in rats treated with contrast media in comparison with control rats. This effect was more evident after diatrizoate but was statistically significant also after iohexol. In conclusion, a reduction in the glomerular filtration rate probably occurs in the first few minutes after contrast media administration. The measurement of urinary excretion of 99mTc-DTPA could be a simple method to detect acute glomerular effects due to contrast media or to other drugs.

Radiocontrast-induced DNA fragmentation of renal tubular cells in vitro: role of hypertonicity.

BACKGROUND: Radiocontrast-induced nephropathy is a clinically important complication of invasive cardiological procedures. It has been associated with DNA fragmentation of renal tubular cells, which is a hallmark feature of programmed cell death (apoptosis). We investigated the mechanism of this DNA fragmentation in an in vitro model of radiocontrast cytotoxicity on renal epithelial cells. METHODS: Madin Darby canine kidney (MDCK) cell monolayers were incubated (for 2-8 h) with isoiodine doses (37-111 mg iodine/ml) of the highly hyperosmolal, ionic radiocontrast agent diatrizoate or of the less hyperosmolal, non-ionic substance iopamidol. Mannitol, urea, and NaCl control media of corresponding hyperosmolality were used to evaluate the contribution of hypertonicity, hyperosmolality and/or ionic strength to radiocontrast toxicity. DNA fragmentation was assessed using fluorescence-activated cell sorting (FACS), agarose gel electrophoresis and terminal deoxynucleotidyl transferase-mediated deoxyuridine nick end labelling (TUNEL), cell morphology was analysed in Giemsa-stained cytospins. RESULTS: Diatrizoate induced concentration- and time-dependent DNA fragmentation of MDCK cells which was associated with morphological signs of apoptosis. Cycloheximide (1 microg/ml) did not prevent diatrizoate-induced DNA fragmentation, indicating that it is not dependent on protein synthesis. Diatrizoate-mediated cell death was associated with cell detachment from the tissue culture matrix. However, the DNA fragmentation is not a consequence of cell detachment since the prevention of cell attachment on agarose-coated dishes induced significantly less DNA fragmentation than diatrizoate. Iopamidol caused no detectable DNA breakdown. In contrast, hypertonic mannitol and sodium chloride, but not hyperosmolal urea, induced DNA fragmentation in MDCK cells, albeit less than diatrizoate. CONCLUSIONS: The DNA fragmentation of MDCK cells induced by diatrizoate is related to its hypertonicity in this in vitro model of radiocontrast cytotoxicity. Nuclear disintegration with subsequent cell death may contribute to the pathophysiology of radiocontrast-induced nephropathy, particularly in the hypertonic/hypoxic environment of the renal medulla. The present results underscore the importance of avoiding hyperosmolal urine states in patients at high risk of radiocontrast-induced nephropathy.

Comparative cytotoxicity of low- and high-osmolar contrast media to human fibroblasts and rat mesangial cells in culture.

RATIONALE AND OBJECTIVES: The authors investigate the relative sensitivity of rat mesangial cells to iodinated contrast media (CM) and control solutions versus less differentiated cells (ie, human fibroblasts) and compare the effects of low-osmolar ionic (ioxaglate) and nonionic (iopamidol) and high-osmolar ionic (diatrizoate) CM on rat mesangial cells. METHODS: The cytotoxic effects of ioxaglate and control solutions of sodium chloride and mannitol were assessed by neutral red uptake in isolated rat mesangial cells and human fibroblasts. In a second series of studies, the cytotoxic effects of ioxaglate, iopamidol, and diatrizoate (0 to 100 mg I/mL) on rat mesangial cells were compared. RESULTS: Rat mesangial cells were more sensitive to the cytotoxic effects of ioxaglate than the less differentiated human fibroblasts between 70 and 100 mg I/mL. A similar discrepancy was observed in the case of control solutions, sodium chloride, and mannitol. Ioxaglate and iopamidol induced a similar level of cytotoxicity in rat mesangial cells whereas the high-osmolar agent diatrizoate was significantly more cytotoxic. However, the calculated inhibitory concentrations of 50% of all three CM were associated with similar osmolalities, suggesting a major role for this parameter in the case of such media. CONCLUSIONS: Rat mesangial cells are more sensitive to the cytotoxic effects of CM and hyperosmolar solutions than the less differentiated human fibroblasts. High-osmolar CM are more cytotoxic than ionic and nonionic low-osmolar CM to rat mesangial cells. Ionicity seems to play no deleterious role at similar iodine concentrations because ioxaglate and iopamidol had equivalent cytotoxic effects on mesangial cells.

Silymarin retards collagen accumulation in early and advanced biliary fibrosis secondary to complete bile duct obliteration in rats.

Silymarin (SIL), a standardized plant extract containing about 60% polyphenole silibinin, is used as a hepatoprotective agent. Its antifibrotic potential in chronic liver diseases has not been explored. Therefore, we applied SIL to adult Wistar rats that were subjected to complete bile duct occlusion (BDO) by injection of sodium amidotrizoate (Ethibloc). This treatment induces progressive portal fibrosis without significant inflammation. Rats with sham-operation that received SIL at 50 mg/kg/d (n = 10) and rats with BDO alone (n = 20) served as controls, whereas groups of 20 animals were fed SIL at a dose of 25 and 50 mg/kg/d during weeks 1 through 6 or doses of 50 mg/kg/d during weeks 4 through 6 of BDO. Animals were sacrificed after 6 weeks for determination of blood chemistries, total and relative liver collagen (as hydroxyproline [HYP]), and the serum aminoterminal propeptide of procollagen type III (PIIINP). BDO in untreated rats caused an almost ninefold increase in total liver collagen (16.1 +/- 3.1 vs. 1.8 +/- 0.4 mg HYP, P < .001). SIL at 50 mg/kg/d reduced total HYP by 30% to 35%, either when given from week 1 through 6 or from week 4 through 6 after BDO (10.6 +/- 2.7 and 10.2 +/- 3.9 mg HYP, both P < .01 vs. BDO alone), whereas 25 mg/kg/d were ineffective. Because SIL at 50 mg/kg/d also reduced the collagen content per gram of liver tissue, it acted as a true antifibrotic agent. The single value of PIIINP at killing paralleled the antifibrotic activity of SIL with 11.6 +/- 3.8 and 9.9 +/- 3.7 vs. 15.3 +/- 5.2 microg/L in both high-dose groups (P < .05 and P < .01, respectively, vs. rats with BDO alone). Except for a decreased alkaline phosphatase and a lower histological fibrosis score in the groups that received SIL, clinical-chemical parameters were not different among all groups with BDO. We therefore conclude that 1) BDO with Ethibloc is a suitable model to test for pure antifibrotic drugs because it induces progressive rat secondary biliary fibrosis without major inflammation; 2) oral SIL can ameliorate hepatic collagen accumulation even in advanced (biliary) fibrosis; and 3) PIIINP appears to be a suitable serum marker to monitor the inhibition of hepatic fibrogenesis in this model of biliary fibrosis.

[Contrast-associated nephrotoxicity: ultrastructural and biochemical study in diabetic rats].

The present study was conducted to determine whether or not the pathologic state of diabetic mellitus serves as a risk factor for the induction of nephropathy by iodinated contrast medium (CM). CM was injected into experimentally induced diabetic rats showing early diabetic nephropathy and these animals were compared with normal rats administered CM. Various types of CM were injected into diabetic rats, and nephropathy was studied morphologically and biochemically. Electron microscopic ultrastructural study revealed vacuolar formation in the cytoplasm of the proximal tubular epithelial cells (PT cells) in both groups. However, some of these changes occurred less frequently in the diabetic group. In the diabetic group, activation of glomerular mesangial cells other than PT cells was observed with amidotrizoate, and retentive deposits in the mesangial areas were found with iopamidol. Biochemical study revealed abnormal values suggesting impaired PT cells in both the diabetic and normal groups. These findings corresponded to the results of electron microscopic ultrastructural observation. The above results suggested the possible occurrence of CM-associated nephrotoxicity in the pathologic stage of diabetic mellitus, even in mild nephropathy.

Comparison of iodinated contrast media-induced renal vasoconstriction in human, rabbit, dog, and pig arteries.

RATIONALE AND OBJECTIVES: Contrast media (CM)-induced renal vasoconstriction is an important factor in the pathogenesis of CM-induced nephrotoxicity. The effects of ionic, high-osmolar CM sodium/meglumine diatrizoate and nonionic, low-osmolar CM iohexol and iopamidol were studied in rabbit, dog, and pig renal arteries and compared with human tissue in an organ bath. METHODS: Isometric contractions were induced by increasing concentrations of CM and high-osmolar glucose solution. RESULTS: Contrast media and glucose elicited contractions in human renal arteries of 32% (diatrizoate), 20% (iohexol), 30% (iopamidol), and 22% (glucose). Rabbit and dog renal arteries demonstrated contractions of 30% and 46% (diatrizoate), 15% and 23% (iohexol), 15% and 26% (iopamidol), and 11% and 40% (glucose), respectively, of the control. There was a vasorelaxing effect of all CM tested on pig renal artery. CONCLUSIONS: Responses in rabbit and dog renal arteries were similar to those in human renal arteries and could serve as models for investigating CM-induced renal vasoconstriction.

The effect of iodine-based contrast agents on the levels of radiation-induced chromosomal aberrations.

The effects of iodine-based contrast agents on the repair of radiation-induced chromosomal damage were investigated employing peripheral blood from a healthy male donor. The blood samples were irradiated with 0.5-4.0 Gy 137Cs gamma rays. Contrast agents and NaCl solutions of various concentrations were added to the blood within the first 15 min or at 60 min after irradiation, and the samples were subsequently cultured for 45 h at 37 degrees C. Significantly elevated frequencies of chromosomal abnormalities caused by postirradiation treatment with hypertonic contrast agents appeared to increase with increasing hypertonicity. Elevated aberration frequencies were found to be greatest in the samples treated within 15 min of irradiation. The contrast agents had little effect if they were added at 60 min after irradiation, probably because the process of chromosome rejoining had been completed. Isotonic iodine-based contrast agents did not enhance the frequencies of chromosomal aberrations to a significant degree.