DIVALENT-CATIONS SUPPRESS 3',5'-ADENOSINE-MONOPHOSPHATE ACCUMULATION BY STIMULATING A PERTUSSIS TOXIN-SENSITIVE GUANINE NUCLEOTIDE-BINDING PROTEIN IN CULTURED BOVINE PARATHYROID CELLS
DIVALENT-CATIONS SUPPRESS 3',5'-ADENOSINE-MONOPHOSPHATE ACCUMULATION BY STIMULATING A PERTUSSIS TOXIN-SENSITIVE GUANINE NUCLEOTIDE-BINDING PROTEIN IN CULTURED BOVINE PARATHYROID CELLS
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DOI：
10.1210/endo-124-1-233
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发表时间：
1989-01-01
期刊：
影响因子：
4.8
通讯作者：
BROWN, EM
中科院分区：
文献类型：
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作者：
CHEN, CJ;BARNETT, JV;BROWN, EM
我们使用百日咳毒素来研究二价阳离子降低牛甲状旁腺细胞cAMP含量的机制。在培养的甲状旁腺细胞中，高细胞外Ca2+ (5 mM)或Mg2+ (5-10 mM)可使多巴胺刺激的cAMP含量降低70-90%。百日咳毒素(0.5 μ。g/ml)完全阻断Ca2+和Mg2+对cAMP含量的抑制作用。Ba2+和Sr2+ (5 mM)也能使cAMP含量降低80-90%，这种作用同样被百日咳毒素阻断。百日咳毒素预处理对cAMP向细胞外液的释放无影响。毒素也没有改变甲状旁腺细胞的磷酸二酯酶活性（42.68 .+-）。3.26 vs. 47.00。2.82 pmol cAMP水解/108个细胞。对照组和毒素处理细胞分别为20分钟)。此外，添加磷酸二酯酶抑制性异丁基甲基黄嘌呤并没有改变对照细胞中5 mM Ca2+对多巴胺刺激的cAMP积累的抑制作用（分别为85%和86%，有和没有异丁基甲基黄嘌呤）。对照细胞匀浆中百日咳毒素催化的ADP核糖基化表明存在mol wt为40K和41K的两种底物。将细胞预先暴露在百日咳毒素中过夜，导致随后用[32P]NAD进行ADP核糖基化的两种底物完全丧失。百日咳毒素预处理并没有通过降低细胞外Ca2+诱导的胞质Ca2+的升高间接增强腺苷酸环化酶的活性，因为百日咳毒素处理的胞质Ca2+水平在5 mM Ca2+处比对照细胞高约60%(531.+- 0.85比326.+- 0.35 nM； P
We used pertussis toxin to study the mechanism(s) by which divalent cations lower cellular cAMP content in bovine parathyroid cells. In cultured parathyroid cells, high extracellular Ca2+ (5 mM) or Mg2+ (5-10 mM) lowers dopamine-stimulated cAMP content by 70-90%. Pertusis toxin (0.5 .mu.g/ml) totally blocks the inhibitory effects of Ca2+ and Mg2+ on cAMP content. Ba2+ and Sr2+ (5 mM) also lower cAMP content by 80-90%, and this effect is, likewise, blocked by pertussis toxin. Pretreatment with pertussis toxin had no effect on the release of cAMP into the extracellular fluid. The toxin also did not modify phosphodiesterase activity in sonicates of parathyroid cells (42.68 .+-. 3.26 vs. 47.00 .+-. 2.82 pmol cAMP hydrolyzed/108 cells .cntdot. 20 min in control and toxin-treated cells, respectively). Moreover, addition of the phosphodiesterase inhibitory isobutyl-methylxanthine did not modify the inhibition of dopamine-stimulated cAMP accumulation by 5 mM Ca2+ in control cells (85% vs. 86% inhibition, respectively, with and without isobutylmethylxanthine). Pertussis toxin-catalyzed ADP ribosylation in homogenates of control cells demonstrated the presence of two substrates with mol wt of 40K and 41K. Preexposure of cells to pertussis toxin overnight resulted in the complete loss of both substrates on subsequent ADP ribosylation with [32P]NAD. Pertussis toxin pretreatment did not enhance adenylate cyclase activity indirectly via reducing the extracellular Ca2+-induced rise in cytosolic Ca2+, since the cytosolic Ca2+ level at 5 mM Ca2+ was about 60% higher in pertussis toxin-treated than in control cells (531.+-.85 vs. 326.+-.35 nM; P