Detection of histidine decarboxylase in rat aorta and cultured rat aortic smooth muscle cells

Objective: Having previously demonstrated release of histamine from mast-cell-deficient rat aorta, the objective of this study was to determine and localize histamine synthe- sis capability in the aorta by detecting histidine decarboxy- lase (HDC), the enzyme that catalyzes histamine formation. Material and methods: Experiments were conducted with nested reverse transcription-polymerase chain reaction (nRT- PCR) to detect HDC mRNA and with immunofluorescence and western blot analysis to detect HDC protein in rat aorta, cultured rat aortic smooth muscle (RASMC) and endothelial cells (RAEC). Results: Gel electrophoresis of nRT-PCR products indicated HDC mRNA in liver, aorta and RASMC but not in RAEC or kidney. Sequence analysis confirmed that the band observed in RASMC was the target HDC amplicon. Immunofluores- cence indicated the presence of HDC protein in RASMC and not in RAEC. Western Blot analysis revealed HDC pro- tein (55 kDa) in liver, aorta, RASMC but not in RAEC or kid- ney. Conclusions: The results of this study are the first to demon- strate the presence of HDC mRNA and protein in rat aorta and more specifically in RASMC, indicative of their capa- bility to synthesize histamine.