Ac polarographic reduction of insulin

Extracellular pH Is Required for Rapid Release of Insulin from Zn−Insulin Precipitates in β-Cell Secretory Vesicles during Exocytosis

“…This amount is in agreement with previous estimates of insulin vesicular content. , The insulin detected is free insulin, dissociated from Zn 2+ , since we have found that the electrode does not detect solubilized Zn−insulin complexes (data not shown). This observation is in agreement with previous studies on the reduction of insulin which showed that complexing of Zn 2+ with insulin inhibits the electroactivity of insulin . The narrow spikes and the amounts detected suggest that a large portion of the Zn−insulin complex dissolved and dissociated rapidly after vesicle opening.…”

“…This observation is in agreement with previous studies on the reduction of insulin which showed that complexing of Zn 2+ with insulin inhibits the electroactivity of insulin. 26 The narrow spikes and the amounts detected suggest that a large portion of the Zn-insulin complex dissolved and dissociated rapidly after vesicle opening. When a similar experiment is performed with cells bathed in pH 6.4 media, no current spikes are detected, as illustrated in Figure 1B, even though flow injection experiments showed that insulin is detectable at this pH.…”