Insulinotropic activity of Tinospora crispa extract: effect on ß-cell Ca2+ handling

The mechanism of insulinotropic action of Tinospora crispa was investigated in vitro using an insulin-secreting clonal ß-cell line, HIT-T15. The aqueous extract sensitizes the ß-cell to extracellular Ca²⁺ and promotes intracellular Ca²⁺ accumulation which in turn causes increased insulin release. The increase in cytosolic Ca²⁺ concentration is due to stimulation of Ca²⁺ uptake from the extracellular medium and inhibition of Ca²⁺ efflux from the cytosol. That the mechanism of insulinotropic action of T. crispa is physiological suggests that the insulin secretagogue/s present in the extract could indeed be a potential source of a specific oral hypoglycaemic agent for the treatment of non-insulin-dependent diabetes mellitus. © 1998 John Wiley & Sons, Ltd.