Abstract
Any devices used in toxicity studies should be validated. In the present study, the physiological conditions of rats implanted with a new micro-infusion pump, iPRECIO®, were examined to evaluate its availability for toxicity studies. Five or six animals/group of 6-week-old male CD(SD) rats received either sham surgery or the implantation surgery for either the iPRECIO® (iP) pump or a standard osmotic infusion pump (OSM) under the back skin. This was followed by 4 weeks (experiment I) or 13 weeks (experiment II) of observation. During the observation period, the iP- and OSM-animals received a continuous infusion of 2.0 or 2.5 μL/hr of saline via the external jugular vein. In experiment I, standard hematologic and blood chemical parameters used in toxicity studies were measured at weeks 1, 2, and 4. The iP-animals showed no abnormal changes in any parameters at any point when compared with the OSM-/SHAM-animals. In experiment II (only iP- and SHAM-animals), necropsy and histopathological examination were performed at weeks 1, 2, 4, and 13. The histopathological examination revealed foreign material-induced inflammatory changes in the dorsal subcutaneous tissue (implantation site) of the iP-animals, including the infiltration of polymorphonuclear or mononuclear cells, edema, granulation and fibrous capsule formation. However, the abnormalities were limited to the implantation site. These results suggest that the implantation of iPRECIO® exerted no significant impact on the physiological condition of the rats. Therefore, we concluded that iPRECIO® is applicable for toxicity studies.
