Altered cytoskeletal organization and secretory response of thrombin-activated platelets from copper-deficient rats

The cytoskeletal organization that occurs following thrombin-induced activation of platelets was investigated in rats consuming either a copper-deficient diet containing less than 1 microgram Cu/g or a copper-adequate diet containing 5.5 micrograms Cu/g. Within 30 s following thrombin activation, the amount of polymerized actin in Triton X-100 extracts of whole platelets from copper-deficient rats was greater than the amount in platelets from copper-adequate rats. Electrophoretic analysis of the cytoskeletal proteins obtained from low speed centrifugation of the Triton X-100 extracts indicated that the myosin content of the cytoskeleton increased with time and reached higher levels following activation in platelets from copper-deficient rats. Actin content of the cytoskeleton also increased with time following activation. However, the difference in cytoskeletal actin content of platelets from copper-deficient and copper-adequate rats was not as great as that observed for myosin. The rate of ATP secretion from thrombin-activated platelets was also increased by copper deficiency. Myosin association with the platelet cytoskeleton may be involved in platelet secretion following thrombin activation. Thus, the increased association of myosin with the cytoskeleton and concomitant increase in ATP secretion suggest that the normal mechanism for stimulus-response coupling is altered in thrombin-activated platelets from copper-deficient rats.