**4.2 Application of the cytokinesis-block micronucleus (CBMN) assay in animal species**

CBMN has been used to determine genomic instability in several models. Initially developed for human lymphocytes [47], it has been tested in other animal models of veterinary interest, such as cow [48–51], goat [52, 53], pig [54–56], rabbit [57, 58], horse [54], rodents [59], hamster cell lines [60], and rodent cell lines [61].


*Sample size (n), Cytokinesis proliferation block index (CBPI), Frequency of binucleated cells with micronucleus (MNi frequency), Number of binucleated cells counted (BN cells Counted).*

*\* Chinese hamster ovary cells (CHO-K1).*

*\*\*L-929 murine fibroblast cell line.*

#### **Table 2.**

*CBMN studies in different vertebrates.*

*Genomic Instability and Cyto-Genotoxic Damage in Animal Species DOI: http://dx.doi.org/10.5772/intechopen.99685*

In most of the published articles presented in **Table 2**, only the MNi number was reported, eight included NDI, and only three took into account other nuclear abnormalities, such as NBUDs [50] and NPBs [49, 60]; no articles that considered the count of cells in necrosis and apoptosis were found.

CBMN is a valuable model for testing genomic instability effects in veterinary pharmacology experiments, such as the one performed in cows to test the mixture of an antiparasitic (cypermethrin) and a pesticide (chlorpyrifos), which reported 16.1 ± 2.3 NBUDs and found no evidence of cytogenotoxicity compared to the gamma radiation exposure [50]. The cytotoxic potential of epoxiconazole and fenpropimorph was also evaluated in bovine lymphocytes, and findings showed no genotoxic effects, however, the cell proliferation index decreased [51]. Moreover, in a trial using the antibiotic enrofloxacin [49], authors found that by increasing the dose, the number of MNi also increased. Another study with dogs analyzed the effect of oral administration of cadmium oxide (10 mg/K), where no significant differences after administration for 3 and 28 days [56] were observed. Finally, it has been reported that loperamide reduces cell proliferation and produces a significant increase in the number of MNi [57].

In general, it has been established that the number of spontaneous MNi in bovines is 3 times higher compared to human lymphocytes [48]. On the other hand, CBMN in goat estimates a better dosimetry fit for gamma radiation than in humans and rabbits. However, pigs and horses also show an excellent dosimetry correlation against X-rays and gamma rays [52, 54, 63].

CBMN has shown that dogs as human pets are excellent sentinels of exposure to environmental factors [55], partly because canine lymphocytes are three times more sensitive than humans to radiation [62].
