Comparison of the effect of NSF-2, scr-NSF-2, NSF-3, and hu-NSF-3 peptides on platelet dense-granule secretion. Platelets with¹⁴C-serotonin–loaded dense granules were preincubated with saponin and different peptides (1 mmol/L) before granule secretion was induced by increasing free Ca²⁺ concentration to 10 μmol/L. Secretion was measured by counting radioactivity in the cell supernatants. The figure shows the percentage of inhibition of secretion by various peptides when granule secretion with no peptide additive is considered as 100% secretion (see Materials and Methods; mean ± SD, n = 4 to 8; platelet samples from 4 different donors).