Glucose-induced proton uptake in secretory granules of beta-cells in monolayer culture.

The weak base acridine orange (AO) has been shown to be accumulated by the insulin-containing secretory granules of cultured beta-cells in response to high glucose. Various lines of evidence indicate that this accumulation is due to a pH gradient. Thus ionophores such as monensin and nigericin abolish the glucose-induced accumulation, and a high concentration of the weak base, benzylamine, results in swelling of the granules. In the absence of glucose, ATP addition to digitonin-permeabilized cells also results in dye uptake. These data also suggest that a primary or secondary active accumulation mechanism for hydrogen ions exists across the granule membrane.