No abstract

The length of the silent lag time before elevation of the cytosolic free Ca2+ concentration ([Ca2+]i) differs between individual pancreatic beta-cells. One important question is whether these differences reflect a random phenomenon or whether the length of lag time is inherent in the individual beta-cell. We compared the lag times, initial dips, and initial peak heights for [Ca2+]i from two consecutive glucose stimulations (with either 10 or 20 mM glucose) in individual ob/ob mouse beta-cells with the fura 2 technique in a microfluorimetric system. There was a strong correlation between the lengths of the lag times in each beta-cell (10 mM glucose: r = 0.94, P < 0.001; 20 mM glucose: r = 0.96, P < 0.001) as well as between the initial dips in [Ca2+]i (10 mM glucose: r = 0.93, P < 0.001; 20 mM glucose: r = 0.79, P < 0.001) and between the initial peak heights (10 mM glucose: r = 0.51, P < 0.01; 20 mM glucose: r = 0.77, P < 0.001). These data provide evidence that the response pattern, including both the length of the lag time and the dynamics of the subsequent [Ca2+]i, is specific for the individual beta-cell.