ELECTRON-PROBE MICROANALYSIS OF CHANGES IN DENSE-BODY PHOSPHORUS AND CALCIUM CONTENT FOLLOWING ALTERATIONS IN PLATELET SEROTONIN LEVELS

Using intact, washed human platelets, we have evaluated dense-body phosphorus and calcium content following procedures which alter total or vesicular serotonin (5-HT) content. Platelet vesicular 5-HT stores were labeled by incubation of platelet-rich plasma (PRP) with [3H]-5-HT, and washed cells were treated for varying time periods with thrombin, the ionophore X537A, or the metabolic poisons antimycin A plus 2-deoxyglucose. After each treatment, [3H]-5-HT remaining in the cells was measured by formaldehyde fixation and scintillation counting. Air-dried whole mounts were prepared from the same cell suspensions, and the calcium and phosphorus content of dense bodies was evaluated by electron microprobe X-ray analysis. A large increase or decrease in vesicular [3H]-5-HT can occur without any measurable change in dense-body calcium or phosphorus. In addition, the loss of [3H]-5-HT, calcium, and phosphorus apparently occurs at different times during platelet incubation with metabolic poisons, suggesting that continued maintenance of vesicular stores of each of the three substrates is linked in a distinct manner to cellular energy production. © 1979.