Boyle J M, Gardner J D
J Clin Invest. 1974 Apr;53(4):1149-58. doi: 10.1172/JCI107653.
We have found that in rat thymocytes binding of [(125)I]choleragen is followed by cellular accumulation of cyclic 3',5'-AMP which, in turn, is followed by stimulation of amino acid transport. Binding of cholera toxin was complete by 30 min and remained constant for the subsequent 150 min. After stimulation by choleragen, cellular cyclic 3',5'-AMP became maximal by 30 min, after which it declined steadily so that by 90 min of incubation, cellular cyclic nucleotide levels were only 20% of those seen at 30 min. Stimulation of amino acid transport, although detectable by 15 min, did not become maximal until 120 min (by which time cellular cyclic 3',5'-AMP had decreased by more than 80%). We have also used this system to delineate the step at which various pharmacologic agents and hormones act to alter the sequence of events mediating the response of rat thymocytes to cholera toxin. The ability of cycloheximide to abolish choleragen-stimulated amino acid influx without reducing [(125)I]choleragen binding or cellular cyclic 3',5'-AMP suggests that cyclic nucleotide stimulation of amino acid transport includes a step involving protein synthesis.
我们发现，在大鼠胸腺细胞中，[(125)I]霍乱原的结合之后是细胞内3',5'-环磷酸腺苷（cAMP）的积累，而cAMP的积累又接着刺激氨基酸转运。霍乱毒素的结合在30分钟时完成，并在随后的150分钟内保持恒定。在霍乱原刺激后，细胞内cAMP在30分钟时达到最大值，之后稳定下降，以至于在孵育90分钟时，细胞内环核苷酸水平仅为30分钟时的20%。氨基酸转运的刺激虽然在15分钟时就可检测到，但直到120分钟才达到最大值（此时细胞内cAMP已下降超过80%）。我们还利用这个系统来确定各种药理剂和激素作用于改变介导大鼠胸腺细胞对霍乱毒素反应的事件序列的步骤。放线菌酮在不降低[(125)I]霍乱原结合或细胞内cAMP的情况下消除霍乱原刺激的氨基酸内流的能力表明，cAMP对氨基酸转运的刺激包括一个涉及蛋白质合成的步骤。
