Voyno-Yasenetskaya T A, Dobbs L G, Williams M C
Institute of Experimental Cardiology, Moscow, USSR.
Am J Physiol. 1991 Oct;261(4 Suppl):105-9. doi: 10.1152/ajpheart.1991.261.4.105.
Several different classes of agonists are known to stimulate exocytosis in type II cells. These agonists cause increases in second messengers, such as adenosine 3',5'-cyclic monophosphate (cAMP) or cytosolic Ca2+, and/or stimulate protein kinase C. We studied generation of cAMP and phosphoinositide (PI) turnover in monolayer cultures of type II cells and measured [Ca2+]i in single cultured cells. ATP [10(-4) M], which stimulates secretion of phosphatidylcholine (PC) and increases cellular cAMP, also stimulated PI turnover and increased [Ca2+]i. 12-O-tetradecanoylphorbol-13-acetate (TPA), which stimulates PC secretion and activates protein kinase C, did not increase [Ca2+]i. Pretreatment of type II cells with the calmodulin antagonist N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) inhibited the PC secretion induced by ATP and TPA and blocked the increase in PI turnover caused by ATP. ATP-dependent surfactant secretion and stimulation of PI turnover could also be inhibited by pretreatment of the cells with pertussis toxin. We used the fluorescent probe indo-1 to measure [Ca2+]i in single cultured type II cells. ATP produced rapid transient increases in [Ca2+]i, which could be prevented by pretreatment of the cells with either TPA or W-7. Our data suggest that pertussis toxin-sensitive G protein(s) are involved in ATP-dependent activation of PI turnover and in secretion of surfactant in type II cells. Activation of protein kinase C blocks the ATP-stimulated increase in [Ca2+]i. Finally, calmodulin may be involved in the regulation of ATP-dependent increase in [Ca2+]i, the activation of PI turnover, and the secretion of surfactant in type II cells.
已知有几种不同类型的激动剂可刺激II型细胞中的胞吐作用。这些激动剂会导致第二信使增加，如3',5'-环磷酸腺苷（cAMP）或胞质Ca2+，和/或刺激蛋白激酶C。我们研究了II型细胞单层培养物中cAMP的生成和磷酸肌醇（PI）的周转，并测量了单个培养细胞中的[Ca2+]i。ATP [10(-4) M]可刺激磷脂酰胆碱（PC）分泌并增加细胞内cAMP，同时也刺激PI周转并增加[Ca2+]i。12-O-十四烷酰佛波醇-13-乙酸酯（TPA）可刺激PC分泌并激活蛋白激酶C，但不会增加[Ca2+]i。用钙调蛋白拮抗剂N-(6-氨基己基)-5-氯-1-萘磺酰胺（W-7）预处理II型细胞可抑制ATP和TPA诱导的PC分泌，并阻断ATP引起的PI周转增加。用百日咳毒素预处理细胞也可抑制ATP依赖性表面活性剂分泌和PI周转刺激。我们使用荧光探针indo-1测量单个培养的II型细胞中的[Ca2+]i。ATP可使[Ca2+]i迅速短暂增加，这可通过用TPA或W-7预处理细胞来预防。我们的数据表明，百日咳毒素敏感的G蛋白参与II型细胞中ATP依赖性PI周转激活和表面活性剂分泌。蛋白激酶C的激活可阻断ATP刺激的[Ca2+]i增加。最后，钙调蛋白可能参与II型细胞中ATP依赖性[Ca2+]i增加、PI周转激活和表面活性剂分泌的调节。
