Nakanishi A, Yoshizumi M, Hamano S, Morita K, Oka M
Department of Pharmacology, Tokushima University School of Medicine, Japan.
Biochem Pharmacol. 1989 Aug 15;38(16):2615-9. doi: 10.1016/0006-2952(89)90546-7.
For determination of whether myosin light-chain kinase (MLCK) is involved in the secretory mechanism of adrenal chromaffin cells, the effect of a preferential inhibitor of the enzyme, 1-(5-chlornaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine (ML-9), on catecholamine secretion from cultured bovine adrenal chromaffin cells was studied. ML-9 did not affect basal catecholamine secretion, but inhibited catecholamine secretion stimulated by acetylcholine, high K+, veratridine or palytoxin. At similar concentrations to those inhibiting the secretion of catecholamine, ML-9 also inhibited increased [45Ca]2+ uptake by the cells induced by these stimulants. However, it did not inhibit catecholamine secretion induced by the Ca2+ ionophore A23187. Moreover, it did not affect catecholamine secretion from digitonin-permeabilized cells induced by a micromolar Ca2+ concentration in the presence of Mg ATP. These results indicate that ML-9 inhibits catecholamine secretion from adrenal chromaffin cells by inhibiting the transmembrane Ca2+ uptake mechanism, but not by inhibiting the intracellular Ca2+-dependent mechanism. The possible role of MLCK in stimulus-secretion coupling in adrenal chromaffin cells is discussed.
为了确定肌球蛋白轻链激酶（MLCK）是否参与肾上腺嗜铬细胞的分泌机制，研究了该酶的一种选择性抑制剂1-(5-氯萘-1-磺酰基)-1H-六氢-1,4-二氮杂䓬（ML-9）对培养的牛肾上腺嗜铬细胞儿茶酚胺分泌的影响。ML-9不影响基础儿茶酚胺分泌，但抑制由乙酰胆碱、高钾、藜芦碱或岩沙海葵毒素刺激引起的儿茶酚胺分泌。在与抑制儿茶酚胺分泌相似的浓度下，ML-9也抑制这些刺激物诱导的细胞对[45Ca]2+摄取的增加。然而，它不抑制由钙离子载体A23187诱导的儿茶酚胺分泌。此外，在Mg ATP存在的情况下，它不影响微摩尔浓度的Ca2+诱导的洋地黄皂苷通透细胞的儿茶酚胺分泌。这些结果表明，ML-9通过抑制跨膜Ca2+摄取机制而非抑制细胞内Ca2+依赖机制来抑制肾上腺嗜铬细胞的儿茶酚胺分泌。本文讨论了MLCK在肾上腺嗜铬细胞刺激-分泌偶联中的可能作用。
