It is important to use the optimal method for repeated blood sampling to ensure minimal stress to mice, and also to provide better pharmacokinetic and pharmacodynamic data. The aim of the present study was to compare the impact of blood sampling methods on corticosterone and adrenocorticotropic hormone (ACTH) levels in mice. Hsdwin:NMRI mice were divided into four sampling groups: control group (I), vena facialis (II), tail vein (III) and saphenous vein (IV). The first blood samples, obtained from vena facialis, tail or saphenous vein of conscious mice, were taken at time point 0. The second blood sample was taken by decapitation from groups II-IV with isoflurane anaesthesia at time point 20 min. The control group animals were anesthetized and decapitated at 20 min time point. Corticosterone levels in plasma were analyzed at time point 0 and 20 min, and ACTH at time point 20 min. Saphenous bled mice, in comparison with vena facialis and tail vein sampled mice, indicated statistically significant greater (P < 0.05) level of corticosterone at sampling point (0 min). Rising levels of corticosterone in all groups differed statistically (P < 0.05) from the control group level, indicating that all tested bleeding methods were stressful to the experimental animals. However, the tail vein bleeding method stressed statistically significantly (P < 0.05) less in comparison with vena facialis and saphenous vein bleeding. At time point 20 min, only saphenous vein bled mice showed statistically significant greater (P < 0.05) blood levels of ACTH compared to tail vein bled mice. Conditions in sampling and rising levels of corticosterone and/or ACTH level did not show direct correlation. In conclusion the results suggest that the tail bleeding method accomplished least stress to mice and next less vena facialis bleeding. Blood collection technique from the saphenous vein was the most stressful to the experimental animals.
