糖皮质激素对单个大鼠肾上腺髓质嗜铬细胞[Ca^(2+)]_i的快速作用

THE RAPID EFFECTS OF GLUCOCORTICOIDS ON INTRACELLULAR CALCIUM CONCENTRATION IN SINGLE RAT ADRENAL MEDULLARY CHROMAFFIN CELLS

为探讨糖皮质激素（glucocorticoids,GC）快速地抑制肾上腺髓质嗜铬细胞（adrenalmedullarychromaffincells，AMCcells）受刺激时分泌儿茶酚胺的机制，用Fura-2作Ca(2+)指示剂．用Spex阳离子测定系统检测单个AMC细胞，观察了对AMC细胞的［Ca(2+)］．的影响。发现皮质酮（B．corticosterone）对AMC细胞静息［Ca(2+)］i无影响，但B可以抑制AMC细胞从无钙介质换到含钙介质时［Ca(2+)］i的升高，可以抑制ACh、Nico（nicotine）、Muse（muscarine）及高钾引起的[Ca(2+)]i升高，RU38486可以部分阻断B对ACh刺激引起的[Ca(2+)]i升高的抑制作用。B还可抑制在无钙介质中Musc引起的［Ca(2+)]i升高。Dex（dexamethasone）与B有相似的作用，而E2(17β-estradiol）、P（progesterone）、Ald（aldosterone）和Andro（androstenedion）无作用。

In order to study the mechanism of the rapid inhibitory effect of glucocorticoids on stimulatedsecretion of catecholamine (CA), we examined the rapid effect of glucocorticoids on [Ca2+ ]i in single rat adrenalmedullary chromaffin cells. Loading chromaffin cells with Fura-2, a fluorescent indicator of free cytosolic Ca2 +,[Ca2+] i were measured with Spex cation measurement system. Although cortionterone did not affect the basal[Ca2+]i of chromaffin cells, it significantly inhibited the increase of [ Ca2+ ]i evoked by acetylcholine, nicotine,muscarine or high K+. RU38486 could partially block the inhibitory effect of corticosterone on the increase of[Ca2+ ]i produced by acetylcholine. The elevation in [Ca2+ ]i evoked by muscarine in the absence of external Ca2+were also inhibited by corticosterone. When cells weretransferred from ca2+-fine medium to normalCa2+ (2. 0 mmol/L) medium, there was usually an ncrease or [Ca2+]i which could also be inhibited bycorticosterone. Dexamethasone had the same inhibitory effect, but 17β--estradiol , progesterone, aldosterone andandrostenedione did not.