The glands, named after the Swiss physician Johann Jakob Harder, are exocrine glands located deep within the orbit. The gland is prominent in rodents and ungulates 2 . The Harderian gland secretes mostly lipids in the rat. Further products include porphyrin and melatonin. The lipid products are similar to those produced by sebaceous glands.
Porphyrins fluoresce under UV light, a trait that readily differentiates it from blood.
This is why we could establish a rapid diagnosis using a Wood s Lamp. The enzyme delta aminolevulinate synthase limits the rate of porphyrin synthesis, and its activity is affected by various factors. For example, in rats, dietary deficiency of panthotenic acid results in high activity and excessive porphyrin production 3 . Various physiological functions have been attributed to the rat Harderian gland. The lipid-containing part of the secretion may serve to lubricate the eye.