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L-Histidine decarboxylase protein and activity in rat brain microvascular endothelial cells
J Yamakami1, E Sakurai, A Kuramasu
1Department of Pharmaceutics I, Tohoku Pharmaceutical University, Sendai, Japan.
Objective And Design:
L-Histidine decarboxylase (HDC) is the primary enzyme regulating histamine biosynthesis. This study was carried out to examine whether the cultured rat brain microvascular endothelial cells (BMEC), which constitute the blood-brain barrier (BBB), have the ability to form histamine, and whether HDC mRNA is expressed in rat BMEC.
Material:
Male, 3-week-old Wistar rats were used. For in vitro studies, rat BMEC were isolated from rat brains, and subculture cells were grown on collagen-coated culture flask and slide.
Methods:
HDC assay, immunofluorescence analysis and expression of HDC mRNA by RT-PCR were performed in rat BMEC.
Results:
The HDC activity of the BMEC was estimated to be 0.14 +/- 0.05 p mol/min/mg protein. This activity was completely inhibited by (S)-alpha-fluoromethylhistidine, a specific inhibitor of HDC. Using a polyclonal anti HDC antibody and immunofluorescence microscopy, we confirmed the presence of HDC protein in rat BMEC. RT-PCR also showed the expression of HDC mRNA in rat BMEC.
Conclusions:
L-Histidine uptaken by rat BMEC was shown to be converted to histamine, suggesting that HDC plays an important role in BBB.