Effects of cation on intracellular pH elevation by induced neurotransmitters on submandibular gland

本研究旨在阐明神经递质诱导唾液腺碱化的机制。将HSG细胞（人颌下腺癌细胞系）和a -431细胞（人表皮样癌细胞系）的细胞加载荧光pH指标BCECF/AM，并在不同浓度（10^<-7>M至10^<-2>M）的神经递质（碳二醇、去甲肾上腺素和异丙肾上腺素）刺激后测量细胞内pH的变化。异丙肾上腺素对任何一种细胞都没有碱化作用，而去甲肾上腺素和甲胆碱对两种细胞的碱化作用浓度范围分别为：10^<-6>M至3*10^<-3>M（去甲肾上腺素作用于HSG细胞），10^<-7>M至2*10^<-4>M（去甲肾上腺素作用于A-431细胞），7*10^<-5>M至10^<-4>M（去甲肾上腺素作用于A-431细胞）。另一方面，在浓度大于6*10^<-5>M时，可以识别出碳醇在HSG细胞中的碱化作用，且碳醇的浓度没有上限。用硝苯地平（100 muM）、Ca^<2+>通道阻滞剂或thapsigargin （100 muM）、amicrosomal Ca^<2+> - atp酶抑制剂进行预孵育，不能消除这种大剂量的碳醇碱化。HSG细胞的碱化系统与其他上皮细胞的碱化系统有很大不同，高剂量乙醇诱导的HSG细胞碱化系统似乎不依赖于细胞内Ca^<2+>。

The aim of this investigation was to clarify the mechanism of alkalization induced by neurotransmitters in human salivary gland. Cells of the HSG cell (a cell line from human submandibular adenocarcinoma) and A-431 cell (a human epidermoid carcinoma cell line) were loaded with a fluorescent pH indicator, BCECF/AM,and the change in the intracellular pH of them was measured following stimulation with various concentrations (10^<-7>M to 10^<-2>M) of neurotransmitters (carbachol, noradrenaline, and isoproterenol). Isoproterenol did not cause alkalization of either cell type at all, whereas, noradrenaline and carbachol alkalized both types over the concentration ranges of 10^<-6>M to 3*10^<-3>M (HSG cell by noradrenaline), 10^<-7>M to 2*10^<-4>M (A-431 cell by noradrenaline), and 7*10^<-5>M to 10^<-4>M (A-431 cell by carbacho1). On the other hand, alkalization induced by carbachol in the HSG cells was recognized at concentrations higher than 6*10^<-5>M,and it showed no upper limit in terms of carbachol concentration. This high-dose carbachol alkalization was not eliminated by preincubation with nifedipine (100 muM), Ca^<2+> channel blocker, or with thapsigargin (100 muM), amicrosomal Ca^<2+> -ATPase inhibitor. The alkalization system of HSG cell was quite different from that in the else epithelial cells and that induced by high-dose carbachol in the HSG cell appears to be independent of intracellular Ca^<2+>.