Preparation and Maintenance of Live Tissues and Primary Cultures for Toxicity Studies

In vitro toxicology consists of using cells or tissues maintained or grown in controlled laboratory conditions to examine the toxic properties of compounds and mixtures. This allows us to examine the toxicity of xenobiotics at the fundamental level of the cell without the interplay of complex physiological systemic effects that are often observed in whole organisms. However, specific cellular functions could be examined with primary cultures of cells from specific tissues such as the liver for xenobiotic biotransformation, kidney or gills for ionic homeostasis, and the nerve cells for neurotransmitter signaling effects. Primary cultures are recognized in maintaining the biochemical make-up of the tissue of origin but for a limited period of time depending on the culture media and conditions. In vitro systems are considered as alternative testing methods to reduce the use of animals in toxicity studies, refine toxicity evaluations (i.e., to go beyond general growth or survival data), and replace in vivo studies—the so-called 3 Rs of alternative tests. Cell- or tissue-based approaches represent a more direct way to determine the mode of action of xenobiotics at the fundamental level. The main advantages of in vitro tests are as follows: (1) reduction of animal sacrifice during toxicity screening of various chemicals, (2) more controlled exposure conditions (hormonal and cofactor make-up of the exposure media), (3) increased precision of the response (less biological variation than with in vivo systems), and (4) high bioanalytical throughput for rapid screening investigations. The mean caveats of in vitro systems are as follows: (1) relevance to in vivo or whole-animal effects (i.e., does a cellular toxicity effect correspond to an effect toward the whole organism?), and (2) loss of systemic effects (e.g., gender- or age-related effects). In this respect, in vitro test systems could represent a powerful tool for toxicity screening and understanding the fundamental mode of action of chemicals provided that the data are related to the whole organism in some way. In this respect, in vitro tests could be validated with the corresponding in vivo model or whole organism with a suite of model toxicants.