Homologous and hybrid calcium complexes of A23187 and hypoglycemic sulfonylureas: nuclear magnetic resonance and conformational analysis.

Hypoglycemic sulfonylureas (e.g., gliclazide) are able to transport calcium across hydrophobic domains. Gliclazide and the ionophore A23187 act synergistically upon calcium transport. One calcium atom is complexed by either two molecules of sulfonylureas (or A23187) or one molecule each of sulfonylurea and A23187; the existence of such hybrid complexes has been documented by nuclear magnetic resonance. Conformation analysis of the calcium-gliclazide complex suggests close apposition of the toluyl groups in the gliclazide molecules.