Oxygen consumption oscillates in single clonal pancreatic β-cells (HIT)

Based on population studies, we have hypothesized that changes in metabolism in pancreatic beta-cells precede changes in Ca2+. It is well known from single-cell Ca2+ studies that variable oscillatory patterns In Ca2+ occur in response to glucose stimulation, The present studies, using the clonal beta-cell line HIT-T-15, were undertaken to evaluate the relationship between glucose concentration, insulin secretion, and O-2 consumption and to determine the Ca2+ dependency of glucose-induced changes in O-2 consumption. In population studies, an excellent correlation was Pound between respiration and insulin secretion, with half-maximal values at similar to 1 mmol/l glucose for both respiration and secretion. In the absence of Ca2+, glucose stimulated O-2 consumption but not insulin secretion. In single clonal beta-cells, a self-referencing O-2 electrode was used to assess O-2 consumption. Large-amplitude oscillations were found to occur in response to stimulation by glucose and were blocked by uncoupling respiration with carbonylcyanide p-(trifluoromethoxy)phenylhydrazone (FCCP). They were also blocked and respiration totally inhibited by antimycin A, an inhibitor of complex III of the respiratory chain. Half of the cells sampled (similar to 100 total) exhibited increased oscillatory O-2 consumption in response to glucose. Oscillations in O-2 occurred in response to glucose even in the absence of Ca2+, and their amplitude increased further on restoration of a normal extracellular Ca2+ level. These studies indicated that; oscillatory O-2 consumption was not dependent on Ca2+ but that the amplitude of the O-2 oscillations increased in the presence of Ca2+, possibly reflecting the additional work involved in insulin secretion and Ca2+ Dumping. These studies demonstrated, for the first time, a direct correlation between O-2 consumption and insulin secretion, the oscillatory nature of O-2 consumption in single cells, and the feasibility of using a highly sensitive noninvasive on-line self-referencing O-2, electrode to monitor single beta-cell respiration.