Shain W, Connor J A, Madelian V, Martin D L
Laboratory of Neurotoxicology and Nervous System Disorders, Wadsworth Center for Laboratories and Research, Albany, New York 12201.
J Neurosci. 1989 Jul;9(7):2306-12. doi: 10.1523/JNEUROSCI.09-07-02306.1989.
Stimulation of beta-adrenergic receptors on LRM55 astroglial cells results in cAMP-dependent release of taurine. We have previously demonstrated that extracellular Ca2+ is not required for either spontaneous or receptor-mediated taurine release (Martin et al., 1988b). In the present series of experiments we investigated the relationship between changes in intracellular free Ca2+ ([Ca2+]i) and taurine release. [Ca2+]i was measured using the fluorescent probe fura-2 and was manipulated by changing the concentration of Ca2+ in the incubation medium and by using the Ca2+ ionophore ionomycin. [Ca2+]i was reduced from 150 +/- 95 nM (n = 46) in control medium (containing 1.1 mM CaCl2) to 46 +/- 10 nM (n = 43) in saline containing no CaCl2 and 10 microM EGTA. [Ca2+]i was rapidly elevated to greater than or equal to 1 microM in medium containing 100 microM CaCl2 and 10 microM ionomycin. Taurine release, either spontaneous or stimulated by isoproterenol, was not significantly affected by these manipulations of [Ca2+]i. [Ca2+]i did not change when cells were stimulated with 100 nM isoproterenol in either control saline containing 1.1 mM CaCl2 or in CaCl2-free saline containing 10 microM EGTA. Other secretogogs (serotonin and ethanol) did not cause changes in [Ca2+]i. These data indicate that neither spontaneous or receptor-mediated taurine release from astroglial cells is Ca2+ dependent. However, when cells were preloaded with Ca2+, allowed to recover briefly, and then stimulated with isoproterenol, it was possible to demonstrate transient increases in Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)
刺激LRM55星形胶质细胞上的β-肾上腺素能受体会导致牛磺酸以cAMP依赖的方式释放。我们之前已经证明，无论是自发性还是受体介导的牛磺酸释放都不需要细胞外Ca2+（Martin等人，1988b）。在本系列实验中，我们研究了细胞内游离Ca2+（[Ca2+]i）变化与牛磺酸释放之间的关系。使用荧光探针fura-2测量[Ca2+]i，并通过改变孵育培养基中Ca2+的浓度以及使用Ca2+离子载体离子霉素来进行调控。在对照培养基（含有1.1 mM CaCl2）中，[Ca2+]i为150±95 nM（n = 46），而在不含CaCl2和含有10 μM EGTA的盐溶液中，[Ca2+]i降至46±10 nM（n = 43）。在含有100 μM CaCl2和10 μM离子霉素的培养基中，[Ca2+]i迅速升高至大于或等于1 μM。这些对[Ca2+]i的调控操作并未显著影响自发性或异丙肾上腺素刺激引起的牛磺酸释放。在含有1.1 mM CaCl2的对照盐溶液或含有10 μM EGTA的无CaCl2盐溶液中，用100 nM异丙肾上腺素刺激细胞时，[Ca2+]i没有变化。其他促分泌剂（血清素和乙醇）也不会引起[Ca2+]i的变化。这些数据表明，星形胶质细胞自发性或受体介导的牛磺酸释放均不依赖于Ca2+。然而，当细胞预先加载Ca2+，短暂恢复后再用异丙肾上腺素刺激时，可以证明Ca2+会出现短暂升高。（摘要截断于250字）
