Expression and cellular localization of melatonin-synthesizing enzymes in the rat lens
Article first published online: 20 OCT 2006
Journal of Pineal Research
Volume 42, Issue 1, pages 92–96, January 2007
How to Cite
Itoh, M. T., Takahashi, N., Abe, M. and Shimizu, K. (2007), Expression and cellular localization of melatonin-synthesizing enzymes in the rat lens. Journal of Pineal Research, 42: 92–96. doi: 10.1111/j.1600-079X.2006.00389.x
- Issue published online: 20 OCT 2006
- Article first published online: 20 OCT 2006
- Received July 10, 2006; accepted September 10, 2006.
- arylalkylamine N-acetyltransferase;
Abstract: Melatonin (N-acetyl-5-methoxytryptamine) prevents oxidative stress-induced cataract development, and previous studies have suggested that the ocular lens synthesizes melatonin. In the present study, we examined whether two key enzymes in melatonin biosynthesis, arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT), are expressed in the lens of adult male rats. Reverse transcriptase-polymerase chain reaction analyses demonstrated that both AANAT and HIOMT mRNAs are expressed in the lens. Western blotting for AANAT protein showed that the lens, like the pineal gland, contains this enzyme protein with a molecular mass of 24 kDa. Immunohistochemistry revealed that AANAT protein is localized to the lens cortical fiber cells. Serotonin, which is a substrate for AANAT and a melatonin precursor, was also found in this region. These findings demonstrate that the lens expresses AANAT and HIOMT, and suggest that the cortical fiber cells are the main melatonin-synthesizing sites in the lens. Locally synthesized melatonin in the lens cortical fiber cells may protect the lens itself from cataract development.