Stimulation of dense tubular Ca2+ uptake in human platelets by cAMP.

作者: Jianguo Tao , Jonas S. Johansson , Duncan H. Haynes

DOI: 10.1016/0005-2736(92)90159-J

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摘要: Elevation of intracellular cAMP is shown to increase the rate (V) and maximal extent Ca2+ uptake by dense tubules in intact human platelets. [cAMP] was accomplished preincubation with adenylate cyclase activator forskolin or dibutyryl-cAMP (Bt2-cAMP). The free concentration tubular lumen ([Ca2+]dt) monitored using fluorescence chlorotetracycline (CTC) according protocols developed this laboratory. cytoplasmic ([Ca2+]cyt) parallel experiments quin2. Both [Ca2+]cyt [Ca2+]dt were analyzed terms competition between pump leak mechanisms plasma membrane (PM) (DT). When platelets are incubated media approx. 1 μM external Ca2+, 50 nM very low. 2 mM added, rises 100 process can be resolved. Forskolin (10 μM) Bt2-cAMP 2.1 ± 0.60 1.70 40 times control values (respectively). agents also final tto 1.72 0.21 Titrations ionomycin (Iono) showed that due an Vm pump. With [Iono] = 500 nM, raised ⩾ 1.0 elicited. (At[Iono]= μM, degraded 15% shunting uptake.) Analysis (1 mM) a factors 1.56 40, respectively. neither agent changed Km significantly from its value 180 nM. Neither constant for passive leakage across DT (1.7 min−1).

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