ABSTRACT
Exocytosis from pancreatic β-cells also exhibits a Ca2+ ion dependence, similar to the other secretory cells described. β-cells secrete insulin based on the level of glucose in the
body, and thus amperometric monitoring of insulin secretion from individual cells is useful in efforts to gain insight into the function of these cells in the regulation of blood sugar levels in the body [20]. Huang et al. have used chromatographic methods to show that the material secreted during exocytosis at these cells is indeed insulin [27]. The fact that insulin is stored within vesicles provides a common link between exocytosis from βcells and from cells of the nervous system. For these reasons, Finnegan et al. have also plotted 228 amperometric spike areas from six human pancreatic β-cells as a Q1/3 histogram (Figure 5) [12]. The distribution of Q1/3 values displays a relative SD (20%) that is almost identical to the previously reported distribution of vesicular radii (21%) [28]. A mean vesicular radius of 150 nm [28] has been used to calculate a mean vesicular insulin concentration of 0.13 M.
