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

我们发现，与烟碱受体激活引起的儿茶酚胺分泌不同，对M受体刺激的分泌反应不是简单地增加钙内流，而是动员猫肾上腺细胞内储存的钙(Nakazato等人，1984)。由于在豚鼠肾上腺中也是如此，与毒鼠碱受体有关的钙离子储存物被认为存在于肾上腺嗜铬细胞中，而不管是哪种。在这个研究项目中，首先，通过使用咖啡因来确定存在与毒碱受体相关的钙离子以外的钙离子的可能性，咖啡因已被认为可以启动钙离子引起的肌肉肌浆网钙离子的释放。其次，研究了亚细胞细胞器对钙蓄积的能力，确定了钙储备的候选者；第三，咖啡因对乙酰基…诱导的钙动员或儿茶酚胺分泌的影响最后，研究了全细胞膜片钳条件下胆碱对膜电流的影响。结果如下：(1)咖啡因引起猫、豚鼠和牛肾上腺嗜铬细胞儿茶酚胺分泌量显著增加；(2)咖啡因的效应被细胞外钙、镁和钠抑制；(3)兰尼定阻断咖啡因的分泌反应，但部分抑制毒鼠碱刺激的反应。(4)内质网和分泌颗粒具有相似的蓄积能力。(5)咖啡因抑制乙酰胆碱、高钾和藜芦碱诱导的儿茶酚胺分泌。(6)乙酰胆碱引起嗜铬细胞烟碱受体电流，去极化诱发电压依赖性钠、钾和钙电流；(7)咖啡因可抑制上述电流。这些结果表明，咖啡因在细胞外钙离子和/或钠离子存在的情况下不能有效地释放儿茶酚胺是由于咖啡因本身对受体连接的离子通道和伏尔盖依赖的离子通道的抑制作用。较少

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