Detection of multiple patterns of oscillatory oxygen consumption in single mouse islets of Langerhans

A novel oxygen microsensor was used to measure oxygen levels in single mouse islets as a function of glucose concentration. Oxygen consumption of individual islets was 5.99 ± 1.17, 9.21 ± 2.15, and 12.22 ± 2.16 pmol/min at 3, 10, and 20 mM glucose, respectively (mean ± SEM, n = 10). Consumption of oxygen was islet-size dependent as larger islets consumed more oxygen than smaller islets but smaller islets consumed more oxygen per unit volume than larger islets. Elevating glucose levels from 3 to 10 mM induced pronounced fast oscillations in oxygen level (period of 12.1 ± 1.7 s, n = 6) superimposed on top of large slow oscillations (period of 3.3 ± 0.6 min, n = 6). The fast oscillations could be completely abolished by treatment with the L-type Ca²⁺-channel blocker nifedipine (40 μM) with a lesser effect on slow oscillations. Slow oscillations were almost completely dependent upon extracellular Ca²⁺. The oxygen patterns closely mimic those that have previously been reported for intracellular Ca²⁺ levels and are suggestive of an important role for Ca²⁺ in amplifying metabolic oscillations.