Figure 5. Ca²⁺ -regulated SY-38 effects on AVP release from permeabilized nerve terminals.

Plot of the relationship between the amount (pg) ± s.e.m. of arginine vasopressin (AVP) released from digitonin-permeabilized neurohypophysial nerve terminals in response to different concentrations of internal Ca²⁺ in the absence (▴) or presence (▾) of 3 μg ml⁻¹ SY-38. There appears to be an interaction or ‘interference’ between the antibody and increasing concentrations of this second messenger. The maximal inhibition of AVP release by SY-38 mAb was observed at 1 μm free [Ca²⁺], but by increasing the Ca²⁺ concentration, less inhibition of AVP release by the SY-38 mAb was obtained.