The temporal relationship of glucose-induced increases in cytoplasmic pH (pHi) and cytoplasmic free Ca2+ was studied in single mouse pancreatic β-cells and suspensions of clonal β-cells (HIT). In both preparations of cells the increase in pHi preceded the cytoplasmic free Ca2+ increase. Therefore the alkalinization cannot be a consequence of the Ca2+ influx. A potential metabolic mechanism for the increase in pHi; involving stimulation of pyruvate transport and oxidation, was demonstrated in a model system of liver mitochondria incubated with pyruvate, ATP, and hexokinase to which glucose was then added to initiate ATP use. The involvement of this mechanism in β-cells is suggested by the observation that the alkalinization was prevented in most cells by incubation with 3-hydroxycyanocinnamate, a mitochondrial pyruvate transport inhibitor. On the other hand, the inhibited cells exhibited normal Ca2+ responses to glucose stimulation. This indicates that neither pyruvate metabolism nor the alkalinization is of critical importance for the Ca2+ signal, though pyruvate oxidation or its metabolites may be important in downstream regulation of secretion.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Biological Chemistry|
|State||Published - 1994|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology