Effects of Various Forms of Stimulation on the Content of Enolase Isozymes and S‐100 Protein in Superior Cervical Sympathetic Ganglia Excised from Rats

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Abstract
Contents of the 3 forms (.alpha..alpha., .alpha..gamma. and .gamma..gamma.) of enolase isozymes and S-100 protein in superior cervical sympathetic ganglia (SCG) excised from rats were determined by the sensitive method of enzyme immunoassay, after application of various forms of stimulation, during incubation for 3 h at 37.degree. C in vitro. The amounts of the 3 forms of enolase isozymes and of S-100 protein in the SCG were not altered by preganglionic or postganglionic stimulation (10 Hz) or by the addition of acetylcholine (1 mM) or a high concentration of K+ (70 mM) to the incubation medium. Norepinephrine (NE; 50 .mu.M), as well as isoproterenol (200 .mu.M) or 3,4-dihydroxy phenylethylamine (dopamine; 200 .mu.M), increased the ganglionic .alpha..alpha. and .alpha..gamma. enolase content to 1.5-2.0 times the control level, whereas NE tended to slightly decrease the .gamma..gamma. enolase content. The increase in the .alpha. isozymes did not appear until after 2-3 h of incubation with this agent as a result of an increase in protein synthesis. Propranolol, an adrenergic antagonist, partly inhibited the NE-induced increase in both .alpha..alpha. and .alpha..gamma. enolases. NE and its agonists also considerably increased the S-100 protein level in the SCG; however, the effect developed within half an hour of incubation as a result of the conversion of the bound S-100 protein to the water-soluble form, and did not greatly increase thereafter. cAMP (1 mM) produced the same kind of increase in the ganglionic S-100 protein content as NE did. Propranolol, as well as cycloheximide, completely suppressed the NE-evoked increase in S-100 protein during 3 h incubation by inducing leakage of the protein into the medium. Axotomy caused greater NE-induced increases in both .alpha..alpha. and .alpha..gamma. enolases and a greater decrease in .gamma..gamma. enolase in the SCG than denervation did, especially if examined 1 or 4 days after the operation. Axotomy alone also produced a delayed rise in NE-induced ganglionic S-100 protein concentration 7 days after the operation. Evidently, there are no interconversions between .alpha..gamma. enolase and the .alpha..alpha. or .gamma..gamma. forms in response to cholinergic stimulation or cell depolarization in the SCG. Instead, NE acts on nonneuronal, glial rather than on neuronal components by increasing the biosynthesis of the .alpha. isozymes of enolase proteins, and NE increases S-100 protein content in nonneuronal, satellite cells through a receptor-mediated, cAMP-dependent solubilization of the bound protein.