L-Histidine decarboxylase protein and activity in rat brain microvascular endothelial cells.
OBJECTIVE
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.


METHODS
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.
Yamakami
J
J
Department of Pharmaceutics I, Tohoku Pharmaceutical University, Sendai, Japan.
Sakurai
E
E
Kuramasu
A
A
Sakurai
E
E
Yanai
K
K
Watanabe
T
T
Tanaka
Y
Y
D000818:Animals; D001812:Blood-Brain Barrier / Q000502:physiology; D001921:Brain / Q000166:cytology / Q000201:enzymology*; D002196:Capillaries / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D006632:Histamine / Q000378:metabolism / Q000494:pharmacology; D006639:Histidine / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D008762:Methylhistidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D004791:Enzyme Inhibitors; D008762:Methylhistidines; D012333:RNA, Messenger; D006639:Histidine; C028309:alpha-fluoromethylhistidine; D006632:Histamine; D006640:Histidine Decarboxylase