Desensitization of sea urchin egg homogenate Ca2+ release by pretreatment with subthreshold concentrations of NAADP or NAADP analogs.
Panel A: Effect of a 9 min pretreatment with buffer (solid line), 1 nM NAADP (1) (dotted line), or 1 nM 5-CH3-NAADP (21) (gray line) on calcium release in response to treatment with 1 μM NAADP. The data has been adjusted along the Y-axis to prevent overlap.
Panel B: Comparison of the abilities of a 9 min preincubation with NAADP (1) or NAADP analogs (16-24) at the stated concentrations to reduce Ca2+ release in response to the addition of 1 μM NAADP. Values shown are mean±SEM (n = 3).