Assistant Laboratory Animal Technician (ALAT) Practice Exam

What causes red staining around the eyes and nose of mice or rats?

1. Hemoglobin

2. Porphyrin

3. Blood serum

4. Melanin

The correct answer is: Porphyrin

Red staining around the eyes and nose of mice or rats is caused by porphyrin, which is a pigment that is produced in the body. Specifically, porphyrins are byproducts of the heme biosynthetic pathway and can be secreted in tears and other excretions, giving a reddish-brown coloration. In rodents, they often accumulate around the eyes and nose due to the excessive production of tears or stress-related conditions. Porphyrin staining is often seen in scenarios where the animal is experiencing discomfort, illness, or is under stress, which can lead to a higher rate of production of these pigments. Additionally, the presence of red-stained fur can indicate an underlying health issue that warrants further investigation by the caregiver. The other options do not contribute to the characteristic staining seen in these animals in the same way that porphyrin does. Hemoglobin is related to blood and typically does not manifest as staining on the fur unless there is bleeding or bruising. Blood serum contains a variety of proteins but does not produce the red staining. Melanin is a pigment that provides coloration to skin and hair, but it does not contribute to red staining specifically associated with secretions in these animals.