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Intrastriatal Grafting of Cos Cells Stably Expressing Human Aromatic l ‐Amino Acid Decarboxylase: Neurochemical Effects
Author(s) -
Kaddis Farida G.,
Clarkson Edward D.,
Weber Michel J.,
Vandenbergh David J.,
Donovan David M.,
Mallet Jacques,
Horellou Philippe,
Uhl George R.,
Freed Curt R.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.68041520.x
Subject(s) - neurochemical , aromatic l amino acid decarboxylase , glutamate decarboxylase , biochemistry , chemistry , carboxy lyases , enzyme , biology , neuroscience
To study the possibility that increasing striatal activity of aromatic l ‐amino acid decarboxylase (AADC; EC 4.1.1.28) can increase dopamine production in dopamine denervated striatum in response to l ‐3,4‐dihydroxyphenylalanine ( l ‐DOPA) administration, we grafted Cos cells stably expressing the human AADC gene (Cos‐ haadc cells) into 6‐hydroxydopamine denervated rat striatum. Before grafting, the catalytic activity of the enzyme was assessed in vitro via the generation of 14 CO 2 from l ‐[ 14 C]DOPA. The K m value for l ‐DOPA in intact and disrupted cells was 0.60 and 0.56 m M , respectively. The cofactor, pyridoxal 5‐phosphate, enhanced enzymatic activity with maximal effect at 0.1 m M . The pH optimum for enzyme activity was 6.8. Grafting Cos‐ haadc cells into denervated rat striatum enhanced striatal dopamine levels measured after systemic administration of l ‐DOPA. When measured 2 h after l ‐DOPA administration, the mean dopamine level in the striata of Cos‐ haadc ‐grafted animals was 2 µg/g of tissue, representing 31% of normal striatal dopamine concentration. The mean dopamine concentration in the striata grafted with untransfected Cos cells (Cos‐ut cells) was 1 µg/g. At 6–8 h after l ‐DOPA administration, striatal dopamine content in the Cos‐ haadc ‐grafted animals was 0.67 µg/g of tissue weight, representing 9% of intact striatum dopamine content. By contrast, the average dopamine content in the Cos‐ut‐grafted animals was undetectable. These findings demonstrate that enhancing striatal AADC activity can improve dopamine bioformation in response to systemically administered l ‐DOPA.