CHARACTERISTIC OF INTRACELLULAR CALCIUM STORES RESPONSIBLE FOR CATECHOLAMINE SECRETION IN ADRENAL MEDULLARY CHROMAFFIN CELLS

我们发现，与烟碱受体激活诱导的儿茶酚胺分泌不同，毒蕈碱受体刺激的分泌反应不仅仅是由于Ca^<2+>内流的增加，而是由于猫肾上腺细胞内储存的Ca^<2+>的动员（Nakazato et al.,1984）。由于在豚鼠的肾上腺中也是如此，因此，与毒蕈碱受体相关的Ca^<2+>储存被认为存在于肾上腺染色质细胞中，无论物种如何。在这个研究项目中，首先，通过使用咖啡因来确定除了与毒蕈碱受体相关的Ca^<2+>储存存在的可能性，已知咖啡因可以启动Ca^<2+>诱导的Ca^<2+>从肌肉肌浆网释放。其次，研究了亚细胞细胞器积累^<45>Ca^<2+>的能力，以确定Ca^<2+>储存的候选物质；第三，研究了咖啡因对Ca^<2+>动员或乙酰胆碱诱导的儿茶酚胺分泌的影响；最后，研究了全细胞膜片钳条件下对膜电流的影响。研究结果总结如下：(1)咖啡因使猫、豚鼠和牛肾上腺嗜铬细胞分泌的儿茶酚胺明显增加；(2)细胞外Ca^<2+>、Mg^<2+>和/或Na^+的存在降低了咖啡因的作用；(3)ryanodine阻断了对咖啡因的分泌反应，但部分抑制了对毒蕈碱刺激的反应。(4)内质网和分泌颗粒对Ca^< 45> ^<2+>的蓄积能力相似。(5)咖啡因可抑制乙酰胆碱、高K^+和缬草碱诱导的儿茶酚胺分泌。(6)乙酰胆碱在嗜铬细胞中引发烟碱受体电流和去极化诱发电压依赖性Na^+、K^+和Ca^<2+>电流；(7)这些电流均被咖啡因抑制。这些结果表明，在细胞外Ca^<2+>和/或Na^+存在的情况下，咖啡因释放儿茶酚胺的无效是由于咖啡因本身对受体连接和电压依赖性离子通道的抑制作用。少

We have found that unlike catecholamine secretion induced by nicotinic receptor activation, the secretory response to muscarinic receptor stimulation is not simply resulting from increase in Ca^<2+> influx,but from mobilization of intracellulary stored Ca^<2+> in cat adrenal glands (Nakazato et al.,1984). Since the same was true in guinea-pig adrenal glands, Ca^<2+> stores linked to muscarinic receptor have been suggested to be present in the adrenal chromaffin cells, regardless of the species. In this research project, first, the possibility of the presence of Ca^<2+> stores other than those linked to muscarinic receptors was determined by using caffeine which has been known to initiate Ca^<2+>-induced Ca^<2+> release from sarcoplamic reticulum of the muscle. Secondly, the ability of subcellular organella to accumulate ^<45>Ca^<2+> was studied to specify the candidate for Ca^<2+> store, thirdly the effect of caffeine on Ca^<2+> mobilization or catecholamine secretion induced by acetyl … More choline and finally, the effect on membrane currents under the condition of whole cell patch clamp were investigated. The results are summarized in the following; (1) caffeine caused a marked increase in catecholamine secretion from adrenal chromaffin cells of cat, guinea-pig and ox, (2) the effectiveness of caffeine was depressed by the presence of extracellular Ca^<2+>, Mg^<2+> and/or Na^+, (3) ryanodine blocked the secretory response to caffeine, but partially inhibited the response to muscarinic stimulation. (4) Both endoplasmic reticulum and secretory granules had the capacity to accumulate ^<45>Ca^<2+> in a similar extent. (5) Caffeine inhibited catecholamine secretion induced by acetylcholine, high K^+ and veratridine. (6) Acetylcholine initiated nicotinic receptor current and depolarization evoked voltage-dependent Na^+, K^+ and Ca^<2+> in chromaffin cells and (7) all of these currents were inhibited by caffeine. These results suggest that the ineffectiveness of caffeine in releasing catecholamine in the presence of extracellular Ca^<2+> and/or Na^+ is due to the inhibitory action of caffeine itself on both receptor linked and volgate- dependent ionic channels. Less