Detection of multiple patterns of oscillatory oxygen consumption in singlemouse islets of Langerhans

A novel oxygen microsensor was used to measure oxygen levels in single mous e islets as a function of glucose concentration. Oxygen consumption of indi vidual 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). Consumpt ion of oxygen was islet-size dependent as larger islets consumed more oxyge n than smaller islets but smaller islets consumed more oxygen per unit volu me than larger islets. Elevating glucose levels from 3 to 10 mM induced pro nounced 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 w ith the L-type Ca2+-channel blocker nifedipine (40 mu M) with a lesser effe ct 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. (C) 199 9 Academic Press.