| Abstrakt: |
Human platelets incubated with Cd took up the cation slowly, and the uptake was speeded up by ionophore A23187. The capacity of human platelets to accumulate Cd was large, equivalent to 10 nmol Cd per mg protein. The effects of Cd on protein phosphorylation and serotonin release of human platelets were studied. Washed platelets incubated with Cd showed a general increase in protein phosphorylation concurrent with a slow release of serotonin. In the presence of ionophore A23187, however, Cd had a biphasic effect on protein phosphorylation: stimulatory at low and inhibitory at high Cd concentrations. The phosphorylation of two proteins with molecular masses close to 43 and 20 kDa was more sensitive to the inhibitory effect of Cd, and under similar conditions, the primary effect of Cd on serotonin release was inhibitory, although at lower Cd concentrations a slight stimulation was noted. Thrombin increased the phosphorylation of several proteins, and a prior incubation with Cd further augmented that of a 20 kDa protein, but this treatment did not affect thrombin-induced serotonin release. [ABSTRACT FROM AUTHOR] |
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