Effect of tetracaine and glibenclamide on ⁴⁵Ca²⁺ handling by isolated pancreatic islets

1

The ⁴⁵Ca²⁺ uptake in β‐cell‐rich ob/ob‐islets was measured using the La³⁺ wash technique.

The ⁴⁵Ca²⁺ uptake in β‐cell‐rich ob/ob‐islets was measured using the La³⁺ wash technique.

Tetracaine (1 mM) markedly enhanced the ⁴⁵Ca²⁺ net uptake (120 min) in the presence of 3 mM glucose, and at 7 and 20 mM glucose there were clear tendencies to dose‐dependent increases with 0.1 to 1 mM tetracaine. Glibenclamide 1 μM to 0.2 mM, stimulated the ⁴⁵Ca²⁺ net uptake in the presence of 3 mM glucose and 0.1 mM to 0.2 mM glibenclamide potentiated the uptake in the presence of 7 mM glucose. When the drugs were added for only a 10 min incubation period, glibenclamide, 1 μM to 0.2 mM, but not tetracaine (10 μM to 1 mM) increased the short‐term uptake of ⁴⁵Ca²⁺. After preincubation with either of the drugs, neither tetracaine (10 μM to 1 mM) nor glibenclamide (10 nM to 0.2 mM) had any effect on the short‐term ⁴⁵Ca²⁺ uptake.

In islets incubated with ⁴⁵Ca²⁺ and tetracaine and washed without La³⁺ the apparent net uptake of ⁴⁵Ca²⁺ was reduced by 0.5 to 1 mM tetracaine both at 3 and 20 mM glucose.

Tetracaine (0.5 mM) stimulated the ⁴⁵Ca²⁺ efflux in the presence of 3 mM glucose.

The results show that both drugs affected the Ca²⁺ handling. It is suggested that glibenclamide mainly increases Ca²⁺ influx by voltage‐dependent pathways, whereas tetracaine, at certain concentrations, mobilizes Ca²⁺ from intracellular stores in the islet cells.

DOI: 10.1111/j.1476-5381.1985.tb08839.x

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