Subchronic Inhalation Toxicity of 1,1,1,3-Tetrachloropropane in Rats

The purpose of this study was to evaluate the inhalation toxicityof 1,1,1,3-tetrachloropropane (TCP), an intermediate in productionof chlorinated silicone fluids. Male and female Sprague- Dawleyrats were exposed 6 hr/day, 5 days/week, for days to TCP atconcentrations of 0, 25, 75, or 225 ppm (Phase study) and to0, 1, 5, or 10 ppm (Phase II study). Phase II of study was conductedbecause a no-observed-effect level was not achieved in PhaseI. No animals died during the study. Clinical signs of toxicityincluded oral, nasal, and/or ocular discharge. No statisticallysignificant differences were observed in either body weightsor food consumption between exposed and control animals. Clinicalpathology did not indicate any treatment related effects. Absoluteand relative liver and kidney weights were increased in maleand female rats exposed to 225 ppm TCP, and heart weights wereincreased in male rats exposed to 225 ppm TCP. The liver andheart weight changes were supported by the findings of microscopiclesions in these organs. These lesions consisted of multifocal/focalmyofiber degeneration necrosis with adjacent chronic myocarditisin the heart and multifocal single-cell necrosis in the liverparenchyma. The liver lesions had essentially resolved at theend of a 28-day recovery period but the heart lesions were stillpresent in male rats in the recovery group exposed to 225 ppmTCP. No treatment-related effects were observed in animals exposedto 1, 5, or 10 ppm TCP. The data of this study showed that theno-observable-effect level for TCP was 10 ppm in male and femaleCD rats.     

CXC and CC chemokines induced in human renal epithelial cells by inflammatory cytokines

Human renal epithelial cells might play an important role during the allograft rejection by producing chemokines in response to proinflammatory cytokines such as tumor necrosis factor (TNF)‐α and interleukin (IL)‐1β produced by endothelial and epithelial cells early after transplantation. The production of chemokines allows inflammatory cells to be drawn into the kidney graft and therefore plays a critical role in the pathophysiologic processes that lead to the rejection of renal transplant. In this process, two chemokine superfamilies, the CC and the CXC chemokines, are the most important. The CC chemokines target mainly monocytes and T lymphocytes, while most of the CXC chemokines attract neutrophils. We showed in our study that in vitro, in unstimulated cells, basal mRNA expression of CXC chemokines (Groα, Groβ, Groγ, ENA‐78 and GCP‐2, IL‐8) that attract neutrophils was detectable and expression of these genes and chemokine release were increased in TNF‐α‐ and IL‐1β‐induced renal epithelial cells. Most of the CC chemokines [monocyte chemotactic protein‐1 (MCP‐1), macrophage Inflammatory protein 1 beta (MIP‐1β), regulated upon activation, normal T cell expressed and secreted (RANTES) and macrophage inflammatory protein (MIP‐3α)] showed detectable mRNA expression only after stimulation with proinflammatory cytokines and not in control cells. TNF‐α seems to induce preferably the expression of RANTES, MCP‐1, interferon‐inducible protein (IP‐10) and Interferon‐Inducible T‐cell Alpha Chemoattractant (I‐TAC), while IL‐1β induces mainly IL‐8 and epithelial neutrophil‐activating peptide 78 (ENA‐78).     

UREA SYNTHESIS AND CYCLOSPORIN A BIOTRANSFORMATION IN A LABORATORY SCALE HEPATOCYTE BIOREACTOR MODEL

Inefficient oxygenation and build-up of waste products are inevitable in a conventional cell culture. The development of a perifusion method for isolated hepatocytes improves the process of oxygenation and helps in end-product removal. For the perifusion of cells, they must be immobilized to prepare a bioreactor model. The present work was directed to testing a hepatocyte bioreactor and maintaining tissue metabolizing activity for periods ranging from 24 to 72 h of continuous and intermittent perifusion and to test the ability of this system for cyclosporin A (CsA), biotransformation and urea synthesis as contrasted to hepatocyte in the culture. Hepatocytes were isolated, immobilized and perifused with William's E culture medium containing 1mM NH(4)Cl and CsA (20 microM). Hepatocytes in the culture were treated in the same way. CsA disappearance from the perifusion or culture media was determined by a HPLC method. Higher urea synthesis rate was achieved by cells in the continuously perifused bioreactor for 24 h compared to culture (0.5+/-0.05 mg h(-1) vs 0.33+/-0.03 mg h(-1), respectively). ALT leakage was lower in the bioreactor model (60 Ul(-1)) as compared to hepatocyte culture (125 Ul(-1)). The ability of hepatocytes in the bioreactor to metabolize CsA was very fast compared to hepatocytes in the culture during 24 h (95% vs 50%, respectively). The present data reveal the higher efficiency of hepatocytes in a bioreactor model as compared to hepatocyte culture. Further research is required in relation to better understanding and standardization of the culture conditions for immobilized and perifused hepatocytes. In addition, the cellular model described here inherits economic and ethical potentials.     

Subchronic Inhalation Toxicity of Tetramethoxysilane in Rats

Sprague-Dawley rats were exposed 6 hr/day, 5 days a week, for28 days to tetramethoxysilane (TMOS) at concentrations of 0,1, 5, and 10 ppm (Phase I study) and to 0, 15, 30, and 45 ppm(Phase II study). All of the rats exposed to 45 ppm TMOS diedor were sacrificed in a moribund state during the 28-day studyperiod. Statistically significant changes were observed in foodconsumption, body weights, and clinical chemistry parametersin the animals exposed to 30 ppm TMOS. Males exposed to 15 ppmTMOS showed a significant decrease in total protein. No effectswere seen in rats exposed to 1, 5, and 10 ppm TMOS. Histopathologicallesions related to TMOS exposure were observed in the respiratorytract tissues and eyes of rats exposed to 15, 30, and 45 ppmTMOS. The principal types of lesions observed were ulceration,inflammation, and necrosis of epithelium. At 45 ppm, changesat these sites were severe and present in all animals. Changesat 30 ppm, while occurring in all rats, were much less severethan those seen at 45 ppm. At 15 ppm, the changes were minimaland occurred only in three males and five females. The dataof this study showed that TMOS has a steep dose-response curvewith no observable effects at 10 ppm, very minimal effects at15 ppm, moderate to severe effects at 30 ppm, and severe effectsand lethality at 45 ppm.