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Low‐Na + Medium Increases the Activity and the Phosphorylation of Tyrosine Hydroxylase in the Superior Cervical Ganglion of the Rat
Author(s) -
Cahill Anne L.,
Horwitz Joel,
Perlman Robert L.
Publication year - 1985
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 - 10.1111/j.1471-4159.1985.tb12868.x
Subject(s) - tyrosine hydroxylase , superior cervical ganglion , tyrosine 3 monooxygenase , ionomycin , tyrosine , stimulation , chemistry , endocrinology , medicine , intracellular , tetrodotoxin , phosphorylation , cholinergic , calcium , dopamine , biochemistry , biology , organic chemistry
Incubation of the rat superior cervical ganglion in Na + ‐free or low‐Na + medium increased the rate of synthesis of 3,4‐dihydroxyphenylalanine (DOPA) in the ganglion fourfold and caused a concomitant stable activation of tyrosine hydroxylase. DOPA synthesis was half‐maximal in medium containing about 20 m M Na + . Low‐Na + medium also increased the incorporation of 32 P i into tyrosine hydroxylase; the dependence of tyrosine hydroxylase phosphorylation on the Na + concentration resembled that of DOPA synthesis. The stimulatory effects of low‐Na + medium on DOPA production and on tyrosine hydroxylase activity in vitro were dependent on extracellular Ca 2+ . The stimulation of DOPA synthesis in low‐Na + medium was inhibited by methoxyverapamil, an inhibitor of Ca 2+ uptake, and was partially blocked by tetrodotoxin, but it was not affected by the cholinergic antagonists hexamethonium and atropine. Ionomycin, a calcium ionophore, stimulated DOPA synthesis to about the same extent as low‐Na + medium and also increased the incorporation of 32 P i into tyrosine hydroxylase. 8‐Bromo cyclic AMP (1 m M ) also stimulated DOPA production in the ganglion, and this stimulation was more than additive with that produced by low‐Na + medium. These data support the hypothesis that low‐Na + medium stimulates DOPA synthesis by raising intracellular Ca 2+ , which then promotes the phosphorylation of tyrosine hydroxylase.