Circular dichroism studies on the interaction of sulfonylureas with insulin.

The interaction of 5 sulfonylurea derivatives with insuline was investigated by means of circular dichroism measurements. It was found that all sulfonylureas investigated decrease the ellipticity band of insulin at 208 nm, whereas the band at 222 nm remains unaffected. It is suggested that these observations are due to a change of the insulin conformation, provoked by the interaction of the drugs with insulin. It is assumed that such an effect on the insulin conformation can influence the binding properties of insulin, e.g. in respect to the insulin aggregation, to the binding to insulin antibodies and to a bound, inactive form of insulin in the plasma. Some other drugs have similar, but mostly smaller effects on the CD spectrum of insulin. Therefore, the importance of these observations for the hypoglycaemic action of the sulfonylureas is not yet clear.