Williams G B, Elder E M, Sussman M
Dev Biol. 1984 Oct;105(2):377-88. doi: 10.1016/0012-1606(84)90294-x.
Using a perfusion technique (P.N. Devreotes, P.L. Derstine, and T.L. Steck, 1979, J. Cell Biol. 80, 291-299), it has been shown that cAMP secretion by aggregation-competent cells in response to an exogenous cAMP signal is significantly reduced by exposure to NH4Cl or any of a set of carboxylic acids that includes propionate, succinate, pyruvate, and acetate. The effects of NH4Cl and any of the carboxylic acids are additive and the combinations restrict cAMP secretion to barely detectable or insignificant levels. The inhibitions are rapidly expressed, and are reversible. The activity of NH4Cl is marked at pH 7.2 and undetectable at pH 6.2. Hence, NH3 is presumably the active molecular species. Propionate activity is significantly greater at pH 6.2 than 7.2, indicating that the un-ionized acid is the active species. The data presented herein indicate that these effects are exerted via two separate and independent routes. During exposure of cAMP-stimulated cells to NH4Cl, the decrease in intracellular cAMP accumulation was even greater than the decrease in extracellular accumulation. Hence, NH3 appears to act as a cAMP accumulation inhibitor (CAI). In contrast, exposure to carboxylic acid concentrations that drastically reduce extracellular cAMP accumulation can actually enhance or, at worst, only slightly reduce intracellular accumulation. Hence, the carboxylic acids appear to act as cAMP release inhibitors (CRI). Stationary phase cells incubated on solid substratum in the presence of NH4Cl plus succinate (or propionate) for 18 hr failed to exhibit even the earliest signs of aggregation. If then harvested and redeposited in the absence of the metabolites, they proceeded through the morphogenetic sequence with approximately normal kinetics, suggesting that no significant morphogenetic competence had been achieved during their previous tenure. The morphogenetic implications of cAMP relay modulation are discussed.
采用灌注技术（P.N. 德夫罗茨、P.L. 德尔斯汀和T.L. 斯特克，1979年，《细胞生物学杂志》80卷，291 - 299页），研究表明，有聚集能力的细胞对外源cAMP信号作出反应时分泌的cAMP，在暴露于氯化铵或一组羧酸（包括丙酸盐、琥珀酸盐、丙酮酸盐和乙酸盐）中的任何一种后，会显著减少。氯化铵和任何一种羧酸的作用是相加的，且这些组合会将cAMP分泌限制到几乎检测不到或微不足道的水平。抑制作用迅速出现且可逆。氯化铵的活性在pH 7.2时显著，在pH 6.2时检测不到。因此，氨可能是活性分子形式。丙酸盐的活性在pH 6.2时比在pH 7.2时显著更高，表明未电离的酸是活性形式。本文提供的数据表明，这些作用是通过两条独立的途径发挥的。在cAMP刺激的细胞暴露于氯化铵期间，细胞内cAMP积累的减少甚至大于细胞外积累的减少。因此，氨似乎作为一种cAMP积累抑制剂（CAI）起作用。相反，暴露于能大幅降低细胞外cAMP积累的羧酸浓度下，实际上可能会增强细胞内积累，或者在最坏的情况下，只会略微降低细胞内积累。因此，羧酸似乎作为cAMP释放抑制剂（CRI）起作用。在氯化铵加琥珀酸盐（或丙酸盐）存在的情况下，在固体基质上孵育18小时的静止期细胞甚至未表现出聚集的最早迹象。如果随后收获并在没有这些代谢物的情况下重新沉积，它们会以大致正常的动力学进行形态发生序列，这表明在它们之前的停留期间没有获得显著形态发生能力。讨论了cAMP信号传递调节的形态发生意义。
