Biotransformation of a somatostatin analogue in precision-cut liver and kidney slices from rat, dog and man

Exploring porcine kidney explants as a model for the study of nephrotoxins and the therapeutic potential of phytic acid

The use of in vivo models to assess nephrotoxicity has faced ethical limitations. A viable alternative is the ex vivo model that combines the 3 R principles with the preservation of tissue histology. Here, we established a gentamicin nephrotoxicity model using pigs` kidney explants and investigated the effect of phytic acid (IP6) against gentamicin- induced nephrotoxicity. A total of 360 kidney explants were divided into control, gentamicin (10 mM), IP6 (5 mM), and gentamicin+IP6 groups. The activity of gammaglutamyltransferase (GGT), creatinine levels, histological assessment, oxidative stress, and inflammatory cytokine expression were analyzed. Exposure to gentamicin induced an increase in GGT activity, creatinine levels, lesion score, lipoperoxidation and IL-8 expression. Explants exposed to IP6 remained like the control. The addition of IP6 to gentamicin prevented tissue damage, increasing the antioxidant status and gene expression of IL-10. This model proved to be an adequate experimental approach for identifying nephrotoxins and potential products to modulate the toxicity.

Influence of Slice Thickness and Culture Conditions on the Metabolism of 7-Ethoxycoumarin in Precision-cut Rat Liver Slices

This study investigated the effects of some experimental variables on the rate of xenobiotic metabolism in precision-cut rat liver slices. Liver slices of 123 ± 8μm (mean ± SEM of six slices), 165 ± 3μm, 238 ± 6μm and 515 ± 14μm thickness were prepared from male Sprague-Dawley rats, and incubated in RPMI 1640 medium in an atmosphere of 95% O2/5% CO2by using a dynamic organ culture system. Liver slices of all thicknesses metabolised 10μM 7-ethoxycoumarin to total (free and conjugated) 7-hydroxycoumarin in a time-dependent manner. The rate of 7-ethoxycoumarin metabolism was greatest in 165μm thick slices and slowest in 515μm thick slices, being 2.74 ± 0.19pmol/minute/mg slice protein and 0.69 ± 0.07pmol/minute/mg slice protein, respectively. No marked effects on the rate of 7-ethoxycoumarin metabolism in liver slices were observed either by changing the medium to Earle's balanced salt solution (EBSS) or by changing the gas phase to 95% air/5% CO2. Moreover, the perfusion of rat livers with EBSS at 2–4°C, prior to preparation of tissue cores, did not enhance 7-ethoxycoumarin metabolism in rat liver slices. In this study, the optimal slice thickness was 175μm, with higher rates of 7-ethoxycoumarin metabolism being observed than with 250μm thick slices, which are often used for studies of xenobiotic metabolism. Variable results were obtained with slices of around 100–120μm thickness, which may be attributable to the ratio between intact hepatocytes and cells damaged by the slicing procedure in these very thin slices.

Liver slices in in vitro pharmacotoxicology with special reference to the use of human liver tissue

In the early years of research in in vitro pharmacotoxicology liver slices have been used. After a decline in the application of slices in favour of the use of isolated hepatocytes and the isolated perfused liver preparation, the development of the Krumdieck slicer in the 1980s led to a ;comeback' of the technique. This review will focus on the use of human liver, with special reference to the comparison of slices with isolated hepatocytes in in vitro pharmacotoxicology. In addition, an overview on the predictive value of these in vitro systems for drug disposition and toxicity in vivo will be given. Preservation techniques for liver slices and hepatocytes will also be discussed. These techniques ensure an efficient utilization of the scarce human material. For long-term storage of liver slices and hepatocytes, cryopreservation seems most promising. However, cryopreservation is still in its infancy, and reports mainly deal with drug metabolism studies after cryopreservation. Drug toxicity, metabolism and transport data determined in slices and isolated hepatocytes, from both human and animal liver showed good correlation with the corresponding parameters measured in vivo. Therefore, the results obtained in such studies may give rise to more in-depth research on the mechanisms of pharmactoxicology in the human liver.

Organ slices as an in vitro test system for drug metabolism in human liver, lung and kidney

Metabolism of xenobiotics occurs mainly in the liver, but in addition, the lungs and kidneys may contribute considerably. The choice of the animal species during drug development as a predictive model for the human condition is often inadequate due to large interspecies differences. Therefore, a universal method for the preparation and incubation of human and animal liver, lung and kidney tissue is being developed for drug metabolism and toxicity testing using precision-cut organ slices. Human tissue was obtained from surgical waste material. Slices were made from rat and human liver, kidney and agar-filled (1.5%, w/v) lung tissue using a Krumdieck tissue slicer and incubated in six-well plates. The morphology and the ATP content show that viability is maintained during 3 hours of incubation. These organ slices show a variety of phase I (hydroxylation, oxidation and O- and N-deethylation) and phase II (glucuronidation and sulfation) metabolic routes using lidocaine, testosterone, 7-ethoxycoumarin and 7-hydroxycoumarin as substrates. The metabolic patterns and rates were found to be different for the various organs and species studied. The use of human tissue slices will enable us to collect more human-specific data on drug metabolism and toxicity. This may lead to a more adequate choice of animal species used during drug development and will result in a considerable reduction in the use of experimental animals.

Viability of liver slices exhibiting absorption, metabolism, and elimination of substrates in culture medium

In an attempt to improve liver slice culture for in vitro tests of newly developed drugs, we found that a relatively thick 2-mm slice was much more viable, long-lived, and metabolically functional than the conventionally used 300-microm-thick slices. Results revealed that some ionic and nonionic compounds (Na(125)I, [(14)C]Ala, and [(14)C]Xyl) dissolved in culture medium were absorbed into the slices, reaching from the cut edges deep into the inner part, in only a short period. Moreover, the slices could be observed for 24 h after incubation so that a normal histological image could be obtained. Each semi-microautoradiographic image was also clearly positive not only at the margin but also in the inner part of each slice. Furthermore, we determined the specific functioning of each donated liver for each substrate added, in uptake, metabolism, and excretion.