Glucose-dependence of insulin secretion rate in perifused islets. Experimental data are for perifused human islets (blue diamonds)  and isolated rat pancreas (blue circles) . Fit of the human data with general Hill-type equations (eq. 2) is shown without any restrictions (best fit, n = 2.7, C Hf,gluc = 6.6 mM; blue line), with restricting the Hill slope to unity (n = 1, Michaelis-Menten-type function, C Hf,gluc = 4.9 mM; dashed blue line), and with the present model used for the local concentration (eq. 6) (n = 2.5, C Hf,gluc = 7 mM; red line).