Stimulation of Amino Acid Uptake and Na+, K+‐ATPase Activity by Norepinephrine in Superior Cervical Sympathetic Ganglia Excised from Adult Rats

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Abstract
Active uptake of a labelled nonmetabolizable amino acid, .alpha.-aminoisobutyric acid (AIB), into isolated superior cervical sympathetic ganglia (SCG) excised from adult rats was considerably stimulated by the addition of either norepinephrine (NE, 50 .mu.M) or 3,4-dihydroxyphenylethylamine (dopamine, DA, 100 .mu.M) to the medium during aerobic incubation for 2 h at 37.degree. C. The NE-induced increase in AIB uptake was significantly antagonized by the addition of an .alpha.1-adrenoceptor antagonist (prazosin, 10 .mu.M) in SCG axotomized 1 week prior to the examination, in which most of the ganglionic neurons had degenerated and reactive proliferation of the satellite glial components was in progress. The addition of neither acetylcholine (ACh, 1 .mu.M) plus eserine (0.1 mM) nor cyclic nucleotides (1 mM) changed the AIB uptake by the SCG. In the axotomized SCG, the NE-evoked increase in AIB uptake was much more pronounced than that of intact or denervated SCG. A kinetic study of active AIB uptake in the SCG showed that NE produced a decrease of the Km value and an increase in the Vmax, especially in the axotomized SCG. Ganglionic Na+, K+-ATPase activity was greatly stimulated in the presence of NE, but not by ACh. These results strongly suggest that the NE-induced enhancement of active AIB uptake in the isolated SCG is occurring in glial cells rather than in neuronal cells, with a possible alteration of membrane properties for amino acid uptake and with an apparent regulation by the stimulated transport enzyme Na+K+-ATPase.

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