In vitro activity: Repaglinide is found to bind with low affinity (K(D)=59 nM) to SUR1 alone, but with high affinity (increased approximately 150-fold) when SUR1 is co-expressed with Kir6.2. Repaglinide binds with low affinity (K(D)=51 nM) to SUR1 co-expressed with Kir6.2DeltaN14. Repaglinide lowers the plasma glucose concentration in the control rat, whilst failing to affect significantly the plasma insulin concentration or insulin/glucose ratio. Repaglinide administration affects neither plasma glucose nor insulin concentration, restores a normal value for the otherwise abnormally high basal insulin output, increases the 16.7 mM/2.8 mM ratio for insulin release, and again augmented protein biosynthesis at both low and high hexose concentrations in Goto-Kakizaki (GK) rats. Repaglinide is found to bind to NCS proteins, but not to CaM or S100 proteins, in a Ca2+-dependent manner. Repaglinide antagonizes the inhibitory action of recoverin in a rhodopsin kinase assay with IC50 values of 400 mM. Repaglinide tightly binds to the visinin-like domain of CCaMK and PpCaMK in a Ca2+-dependent manner and antagonizes the regulatory function of the domain with IC50 values of 55 and 4 mM for CCaMK and PpCaMK respectively.