INTERACTION BETWEEN MUSCARINIC AND NICOTINIC RECEPTORS IN CATECHOLAMINE SECRETION FROM ADRENAL MEDULLARY CELLS

众所周知，肾上腺嗜铬细胞同时具有参与乙酰胆碱诱导儿茶酚胺分泌的M受体和烟碱受体。我们发现，与烟碱受体激活诱导的儿茶酚胺分泌不同，M受体介导的分泌反应不是由于钙内流增加，而是由细胞内某些储存部位的钙动员引起的。本实验研究了(1)M受体与烟碱受体相互作用引起儿茶酚胺分泌的方式，(2)与M受体相连的细胞内Ca~(2+)的性质，以及(3)该假想的Ca~(2+)释放机制。为此，我们使用了猫和豚鼠的肾上腺灌流，分离的狗和豚鼠的肾上腺嗜铬细胞和培养的牛肾上腺嗜铬细胞。主要结果如下：1.Pr…可显著增加烟碱(5×10~(-1)~(-5)~(-5))引起的儿茶酚胺分泌量更多的是应用一种纯粹的毒鼠碱激动剂，奥曲莫林(10^&lt；-5&gt；M)，它本身只引起很小的分泌反应。因此，当乙酰胆碱从肾上腺嗜铬细胞释放儿茶酚胺时，尼古丁和毒扁豆碱受体似乎相互作用。肾上腺嗜铬细胞似乎至少有两个不同的钙离子储存区，负责儿茶酚胺的分泌，一个对咖啡因敏感，另一个对M受体的激活敏感，第二信使已知是IP_3。两个储存区似乎有部分重叠。与平滑肌细胞类似，咖啡因敏感的储存库建议在开放状态下被兰诺定锁定。这些结果表明，钙诱导的钙释放机制与肌细胞一样存在。已证实咖啡因和乙酰胆碱可引起Fura 2-AM负载的培养牛肾上腺嗜铬细胞胞浆游离钙离子浓度升高。兰尼定选择性地阻断咖啡因引起的钙离子浓度升高。较少

It is well known that adrenal chromaffin cells possess both muscarinic and nicotinic receptors involved in acetylcholine-induced catecholamine secretion.We have found that unlike catecholamine secretion induced by nicotinic receptor activation, muscarinic receptor-mediated secretory response was not a result of increased Ca^<2+> influx, but of mobilized Ca^<2+> from some intracellular storage sites. In this experiment, the study was made about, (1) the mode of interaction between muscarinic and nicotinic receptors in causing catecholamine secretion, (2) the nature of intracellular Ca^<2+> store linked to muscarinic receptors and (3) Ca^<2+> releasing mechanism from that hypothetical store. For this purpose, we used perfused adrenal glands of cat and guinea pig, isolated adrenal chromaffin cells of dog and guinea pig and cultured bovine adrenal chromaffin cells. The results are summarized as follows: 1. Catecholamine secretion evoked by nicotine (5xlO^<-5>M) was markedly increased by pr … More eceding application of a pure muscarinic agonist, oxotremorine (10^<-5>M) which caused only a minute secretory response by itself. It appears therefore that both nicotinic and muscarinic receptors interact with each other when acetylcholine releases catecholamine from adrenal chromaffin cells.2. Adrenal chromaffin cells seem to possess at least two different Ca^<2+> stores responsible for catecholamine secretion as suggested in smooth muscle cells.One is sensitive to caffeine and the other one is to muscarinic receptor activation of which the second messenger is known to be IP_3. There appears to be a partial overlap in both stores. Similar to that of smooth muscle cells, caffeine-sensitive stores are suggested to be locked by ryanodine in open state. These results suggest that Ca^<2+>-induced Ca^<2+> release mechanism is present as it is in muscle cells.3. It was confirmed that caffeine and acetylcholine cause increase in cytosolic free Ca^<2+> concentration in cultured bovine adrenal chromaffin cells loaded with Fura 2-AM. Ryanodine selectively blocked the caffeine-induced Increase in the Ca^<2+> concentration. Less