Acetylcholine (ACh) is present in human blood and localized in T-lymphocytes which exhibit ACh-synthesizing activity. As the final step towards clarifying the origin of ACh present in the blood, we elucidated the enzyme involved in ACh synthesis in T-lymphocytes by detecting the mRNA for choline acetyltransferase (ChAT), which is known to catalyze ACh synthesis in the nervous system. The ChAT mRNA in the MOLT-3 human leukemic T-cell line was amplified by reverse transcription-polymerase chain reaction (RT-PCR) using specific order and reverse primers. A single specific RT-PCR product was observed on agarose gel. The sequence of the RT-PCR product of MOLT-3 was completely identical with nucleotide positions 322–973 of human brain ChAT cDNA. Western blot analysis with an antibody to ChAT confirmed the presence of ChAT protein in MOLT-3. These findings demonstrate that mRNA for the same ChAT as that in the nervous system is expressed in T-lymphocytes, and indicate that ACh synthesized by ChAT in T-lymphocytes is the origin of ACh in the blood.
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