Gray D C, Ginsborg B L, House C R
Q J Exp Physiol. 1984 Jan;69(1):171-86. doi: 10.1113/expphysiol.1984.sp002778.
Isolated salivary glands of the cockroach Nauphoeta cinerea Olivier secrete fluid in response to nerve stimulation or application of dopamine, the acinar cells undergoing a hyperpolarization during secretion. The aim of the present work was to examine whether cyclic AMP acts as a second messenger in the acinar cells to cause the secretory and electrical responses to the transmitter dopamine. Cyclic AMP (10-500 microM) in the bathing solution of isolated glands caused a dose-dependent secretory response but no change in the membrane potential of acinar cells. The time courses and magnitudes of the secretory responses to cyclic AMP resembled those features of responses to dopamine. Forskolin, an adenylate cyclase activator, caused fluid secretion but the responses were small and irregular. The phosphodiesterase inhibitor, 3-isobutyl-l-methylxanthine (IBMX)(1-1000 microM) produced fluid secretion in a dose-dependent manner, the maximal response being equal to that of dopamine. Maintained responses to cyclic AMP or IBMX required the presence of extracellular calcium ions. An inhibitor (MDL 12,330A) of adenylate cyclase suppressed the secretory responses to dopamine, cyclic AMP, IBMX, the ionophore A23817 or the readmission of calcium ions to the bathing solution; this inhibitor did not block the acinar hyperpolarization caused by nerve stimulation. Cyclic AMP stimulation of glands, bathed in chloride-free solution to prevent fluid secretion, produced a change in the gland cells which outlasted the period of exogenous cyclic AMP stimulation and expressed itself as a transient secretion upon return of the normal bathing solution. It was concluded that stimulus-secretion coupling in this gland involves a calcium-dependent second messenger system and that cyclic AMP is probably the second messenger. The evidence did not support the idea that cyclic AMP is also a second messenger for the acinar cell hyperpolarization evoked by nerve stimulation.
将蜚蠊（Nauphoeta cinerea Olivier）的单个唾液腺分离出来，当受到神经刺激或施加多巴胺时，这些唾液腺会分泌液体，腺泡细胞在分泌过程中会发生超极化。本研究的目的是检验环磷酸腺苷（cAMP）在腺泡细胞中是否作为第二信使，从而引发对递质多巴胺的分泌和电反应。在分离腺体的浴液中加入环磷酸腺苷（10 - 500微摩尔）会引起剂量依赖性的分泌反应，但腺泡细胞膜电位无变化。对环磷酸腺苷分泌反应的时间进程和幅度与对多巴胺反应的这些特征相似。腺苷酸环化酶激活剂福斯高林可引起液体分泌，但反应较小且不规则。磷酸二酯酶抑制剂3 - 异丁基 - 1 - 甲基黄嘌呤（IBMX）（1 - 1000微摩尔）以剂量依赖性方式产生液体分泌，最大反应与多巴胺的相同。对环磷酸腺苷或IBMX的持续反应需要细胞外钙离子的存在。腺苷酸环化酶抑制剂（MDL 12,330A）可抑制对多巴胺、环磷酸腺苷、IBMX、离子载体A23817或向浴液中重新加入钙离子的分泌反应；该抑制剂不会阻断由神经刺激引起的腺泡超极化。用无氯溶液浸泡腺体以防止液体分泌，在此条件下用环磷酸腺苷刺激，会使腺细胞产生一种变化，这种变化在外源性环磷酸腺苷刺激期过后仍持续存在，并在恢复正常浴液时表现为短暂分泌。得出的结论是，该腺体中的刺激 - 分泌偶联涉及一个钙依赖性第二信使系统，环磷酸腺苷可能就是第二信使。证据不支持环磷酸腺苷也是神经刺激引起腺泡细胞超极化的第二信使这一观点。
