Concentration-dependent inhibition of platelet dense-granule secretion by NSF-2 peptide in permeabilized human platelets. Platelets with ¹⁴C-serotonin–loaded dense granules were preincubated with saponin and various concentrations of NSF-2 peptides or with no peptide addition. Granule secretion was induced by increasing free Ca²⁺-concentration to 10 μmol/L. Secretion was measured by counting radioactivity in the cell supernatants (see Materials and Methods; mean ± SD, n = 2).