Effects of an individually ventilated cage system on the airway integrity of rats (Rattus norvegicus) in a laboratory in Brazil.

The ventilation method used in the management of laboratory rats is important in maintaining their health. Rats kept under general diluting ventilation (GDV) are exposed to high levels of pollutants present in the environment (dust, airborne bacteria, etc.) or those pollutants produced by animal metabolism and excretion inside the boxes (e.g. ammonia and carbon dioxide). These pollutants may contribute to respiratory pathologies. An alternative experimental ventilation system for laboratory animal housing using intracage ventilation technology (individually ventilated cage system, IVC) was developed. In this system, ammonia levels decreased and rats exhibited better reproductive performance and a lower incidence of pneumonia than rats maintained under GDV. Using two different levels of air speed (0.03-0.26 m/s: IVC(1); 0.27-0.80 m/s: IVC(2)), the effects of IVC were compared with GDV (control) in Wistar rats in terms of respiratory mucus properties, on the nasal epithelium (as measured by quantitative morphometry) and on the lungs (as determined by the cellular composition obtained by bronchoalveolar lavage). Mucus of the respiratory system was evaluated using the following techniques: rheology (viscoelasticity) by microrheometer, in vitro mucociliary transportability (frog palate) and contact angle (an indicator of adhesivity). Also, membrane transepithelial potential difference was measured as a biomarker of airway integrity. After bedding was changed, ammonia concentrations inside the cages on day 3 were significantly higher for GDV than for IVC(1) and IVC(2). The potential-difference values for IVC(1), IVC(2) and GDV in the epiglottis and in the trachea also showed differences. Although some significant differences were observed across the three groups in counts of some cell types, the intragroup results were highly variable among individuals and inconsistent between sexes. No significant differences in the other parameters were found across groups. These results establish that rats maintained under GDV in relatively unregulated conditions are exposed to factors that can lead to deleterious effects on the ciliated epithelium of the airways, and that these effects can be prevented by the use of IVC.

Laboratory Animal Legislation in Latin America.

A review of existing legislation covering laboratory animals in Latin America is presented. The region presents a spectrum of economic development, political stability, and cultural diversity. With the exception of a few nations, there is a lack of regulations as well as minimal enforcement of existing laws pertaining to laboratory animals. Brazil, Mexico, and Uruguay stand out as the only nations in this region with specific legislation regulating laboratory animal care and use; the history and current status of regulations in these three nations is reviewed.

Evaluation of reproductive indices in rats (Rattus norvegicus) housed under an intracage ventilation system.

A cabinet with an intracage ventilation system (ICV) was developed, and rats (Rattus norvegicus) were exposed to five air-speed levels (ICV 1, 0.03 to 0.12 m/s; ICV 2, 0.13 to 0.18 m/s; ICV 3, 0.19 to 0.33 m/s; ICV 4, 0.34 to 0.51 m/s, and ICV 5, 0.52 to 0.80 m/s) to evaluate optimal rates for ventilation and to assess whether reproductive performance differed at the various air speeds. Our results showed that rats housed under ICV conditions tolerate a continuous air flow into the cage. This condition did not impair the reproductive performance in any of the groups. In fact, air-speed levels ranging from 0.19 to 0.51 m/s (ICV3 and ICV4 conditions) led to a greater number of and more uniform litters with decreased mortality rates compared with those of the control group.