Preliminary observations on Sister Chromatid Exchange (SCEs) induced by high dosage of BrdU in metaphase chromosomes of the Agerolese breed of cattle (Bos taurus).

The present study reports on Sister Chromatid Exchanges (SCEs) in lymphocytes of the Agerolese breed of cattle exposed to BrdU dosages of 10 and 300 μg/ml, (f.c.) for two cell cycles. Peripheral blood was drawn from 3 healthy cows, and cultured in duplicate for 72 hours in RPMI 1640 medium plus 10 % FBS, L-glutamine, antibiotic-antimicotic, and Concanavalin-A. After 36 hours from the initiation, BrdU (Sigma) was added to the cultures, respectively at 10 μg/ml and 300 μg/ml (f.c.). Slides were stained with acridine orange solution (0.010 % in Sorensen buffer, pH=7.0). 20 metaphases were analyzed for each animal, for each dosage, with a total of 3,523 chromosomes. The mean rate of SCE/cell was 5.85 ± 2.71 at the dosage of 10 μg/ml while it increased up to 33.93 ± 13.03 at the dosage of 300 μg/ml. The fraction of chromosomes ‘with’ exchanges was only 9 % at the dosage of 10, while it increased up to 41.51 % at the dosage of 300. The exchanges (SCEs) observed at 10 μg/ml were of type 1 (8.84%), type 2(0.42 %) and type 3 (0.03 %), whereas at 300 μg/ml many more exchanges were observed as follows: type 1 (29.10 %), type 2 (9.54 %), type 3 (1.98 %), type 4 (0.77 %), type 5 (0.09 %) and type 6 (0.03 %). By increasing the BrdU final concentration from 10 to 300 μg/ml , the total number of exchanges visualized rised from 354 at 1,462 (4.13 times). These results encourage further insights into the SCE studies at high dosages of BrdU in order to better characterize the genome stability in the livestock species and breeds engaged in animal production.