Refinement of blood sampling from the sublingual vein of rats

A refined method of repeated blood sampling is described: the tongue of the anaesthetized rat is pulled forward with the fingers and the sublingual vein is punctured with a 23 gauge hypodermic needle. Based on the requirement of a pharmacokinetic study, 0.5 or 1 ml of blood was collected 7 times at 0, 0.5, 1, 2, 4, 8 and 24 h. The degree of suffering was judged by determining the body weight and food and water consumption. All animals showed an increase in body weight already after 24 h and, therefore, the method of collecting blood from the sublingual vein can be recommended for repeated blood sampling. The haematological evaluation of groups of animals with differing body weight showed that sample volumes of up to 15% of the total blood volume lead to haematocrit values of approximately 40%. A remarkable initial drop in white blood cell counts followed by a marked rise 2 h after first sampling to values partly above the pre-test could not be directly related to the extracted blood volume.