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.

Pharmacologic profile of iobitridol, a nonionic iodinated contrast medium.

The present article combines and summarizes the preclinic studies carried out in vitro and in vivo to determine the pharmacologic and biochemical profile of iobitridol, a new nonionic iodinated low-osmolality contrast medium (CM). The effects of this product on the main hemodynamic, bronchopulmonary, neurologic, renal, blood chemistry and electrophysiologic parameters and RBC morphology were studied in detail in comparison with CM in the same chemical category or with reference substances of the same osmolality. The in vivo studies were performed under conditions resembling clinical use. Iobitridol showed an excellent pharmacologic and biochemical profile, which was identical or superior to that of other products in its category.

Inhibition of cyclosporin-induced in vitro glomerular contraction by theophylline.

Cyclosporin A (CsA) induces in vivo severe nephrotoxicity characterized by a large decrease in renal haemodynamics. The aim of this study is to show the ability of theophylline, a xanthic derivative, to diminish the CsA-induced vasoconstrictive effects by using two in vitro rat glomerular models, for example isolated glomeruli and cultured mesangial cells. Isolated glomeruli are obtained from the superficial renal cortex of male Sprague-Dawley rats by a sieving method. Mesangial cells are cultured in RPMI 1640 medium with 15% foetal calf serum (FCS). The area of either isolated glomeruli or mesangial cells is assessed by an image analyser with a video camera. Each glomerulus or mesangial cell serves as its own control by photographing them before any drug incubation and after incubation for 10, 20 and 30 min either in control solution or control solution with CsA or CsA and theophylline. CsA (10(-6)m) induces an important time-dependent decrease in the glomerular area (about 13.4% after 30 min). When theophylline is added only a slight decrease is noticed (about 3.4% after 30 min). The same results are obtained with mesangial cells. In conclusion, a direct vasoconstrictive effect of CsA in isolated glomeruli and mesangial cells can be confirmed. In addition, this effect can be partially prevented by theophylline.

Image analyser as a tool for the study of in vitro glomerular vasoreactivity.

Many drugs used in clinics can dramatically reduce renal hemodynamics. For some years there have been developed in our laboratory two in vitro glomerular models, isolated glomeruli and mesangial cell cultures, to quantitate, by video image analyzer, the direct glomerular effect of vasoreactive agents. The present study shows the vasoconstrictive effects of angiotensin II and cyclosporin in both models and compares their glomerular vasoconstriction with or without vasodilating agents such as verapamil. This drug-induced glomerular vasoreactivity is time- and dose-dependent; moreover, it can be reversible after perfusion in control conditions. The interest of these in vitro glomerular models is validated by fair correlations between in vivo and in vitro data and between the responses of both. These models can be considered as tools for assessing glomerular vasoreactivity of nephrotoxic agents.

Protective effect of verapamil in cyclosporin-incubated human and murine isolated glomeruli.

Cyclosporin A (CsA)-induced nephrotoxicity is characterized by a decrease in the glomerular filtration rate (GFR) which is associated with a large increase in renal vascular resistance (RVR). Using a video image analyzer, we have demonstrated CsA-induced glomerular vasoconstriction in rat isolated glomeruli as assessed by a significant reduction of glomerular area. This vasoactive response explains in part the renal hemodynamic changes and the development of CsA-induced reversible decline in renal function. To confirm the direct vasoactive effect of CsA on glomeruli and to determine if calcium-blocking agents modified this response, we compared the changes in area of isolated rat and human glomeruli incubated either with CsA alone or with CsA plus verapamil. The area of the isolated glomeruli was quantitatively evaluated by a camera video image analyzer; each glomerulus served as its own control. Area kinetics were studied at 5 min intervals over 30 min. CsA-induced glomerular size reduction is dose dependent (-4.2% for 10(-10) M and -10.2% for 10(-6) M) and time dependent (-2.3% at 5 min, -4.7% at 10 min, and -12.1% at 30 min for 10(-6) M). With verapamil pretreatment, CsA-induced reduction in glomerular size was reduced (-0.6% and -3.6%, respectively, for 10(-6) M and 10(-7) M verapamil). Thus, verapamil can be considered as a protective agent against CsA-induced vasoconstriction in rat and human isolated glomeruli.

[Protective effect of verapamil and dopamine against cyclosporine-induced vasoconstriction in isolated glomeruli in rats]. / Effet protecteur du vérapamil et de la dopamine à l'égard de la vasoconstriction induite par la ciclosporine sur glomérules isolés de rat.

Cyclosporin A (CsA)-induced nephrotoxicity is characterized by dramatic changes in glomerular filtration rate and renal plasma flow, largely limiting the clinical use of this drug. The vasoconstrictive response of CsA could explain, in part, these hemodynamic alterations. The present study compares the area changes in rat-isolated glomeruli incubated with CsA alone or after pre-treatment with verapamil and dopamine. In verapamil-pretreated CsA-intoxicated glomeruli, size decrease was reduced (-1.5 percent at T10, -3.1 percent at T20 and -4.8 percent at T30), when compared with CsA alone (-4.7 percent at T10, -10.1 percent at T20 and -12 percent at T30). The results obtained with dopamine were similar. In conclusion, verapamil and dopamine can be regarded as fair protective agents against CsA-induced vasoconstriction in rat-isolated glomeruli.

[Effect of verapamil on cyclosporine-induced vasoconstriction in human or murine isolated glomerules]. / Influence du vérapamil sur la vasoconstriction induite par la ciclosporine sur glomérules isolés humains et murins.

Cyclosporin is a very potent immunosuppressant, but it often produces renal disturbances which limit its clinical use. Using an image analyzer which determines the areas of isolated glomerules, we were able to demonstrate that cyclosporin in various concentrations exerts a direct vasoconstrictive effect on human and murine glomerules. We also showed that verapamil has an almost total inhibitory effect on cyclosporin-induced vasoconstriction. These findings seem to be of interest in clinical practice to reduce the nephrotoxicity of cyclosporin.

Correlation and validation of alternative methods to the Draize eye irritation test (OPAL project).

A multicentre study of alternative methods to the Draize eye irritation test, involving six different laboratories was organized by OPAL (Oeuvre Pour l'Assistance aux Animaux de Laboratoire). Forty chemicals (including solvents, surfactants, acids, bases, and others) were selected for testing by three methods, namely Griffith's test (a low-volume eye irritation test on rabbits), the hen's egg chorioallantoic membrane (HET-CAM) assay for the evaluation of hyperaemia, haemorrhage and coagulation, and neutral red uptake by SIRC cells for the assessment of cytotoxicity. Each method was used in two or three laboratories. Intralaboratory reproducibility was good for each laboratory with values, for error, close to 10%. Interlaboratory agreement was also good, particularly for the cell culture method, a quantitative and objective technique. Griffith's test correlated well with the Draize test (r = 0.846; n = 37), while for the HET-CAM test (r = 0.670; n = 32) and the cell culture method (r = 0.579; n = 32) the correlation was satisfactory. A more complete statistical analysis is currently under way to confirm and extend these preliminary findings.

[Demonstration of direct vasoconstrictive effect of cyclosporin on glomeruli isolated from human kidney]. / Mise en évidence de l'effet vasoconstricteur direct de la cyclosporine sur glomérules isolés de rein humain.

Cyclosporin (CsA), a potent immunosuppressive agent, can induce severe renal damage, characterized by lesions in the tubulo interstitial region and decreased renal function. Isolated glomeruli can be considered as a fruitful model to evidence the direct effect of drugs at the level of glomerular structures. The present study aims to evidence, in this model, vasoactive response of isolated human renal glomeruli induced by different CsA concentrations. Area changes of such isolated glomeruli can be assessed by a semi-automatic morphometric method, using a video-camera device coupled with a microprocessor (Biocom 2000). Experiments are done under double bind conditions. CsA-induced decrease in glomeruli area is dose- and time-dependent. CsA effect is rapid in that glomerular area is significantly decreased even after 5 min. incubation; vasoconstrictive effect is more important (and maximum) after 10 min. incubation; significant decrease can be noted with 10(-7) M (-11.41%) and 10(-6) M (-10.26%). In conclusion, the isolated glomerulus model allows us to demonstrate the direct vasoconstrictive effect of CsA, that can in part explain the renal functional changes and the acute renal failure often described in human clinic.