Quality control of insulin radioreceptor assay for human erythrocytes. Effect of ageing of mono- ¹²⁵I-Tyr-A14-insulin preparation

Abstract

The quality control of insulin radioreceptor assay for human erythrocytes is based on the storage of erythrocyte preparations in Hepes buffer of pH 8.0, containing 10 g/l of albumin and 20 mmol/l of glucose. The change of erythrocytes into spherocytes and crenated cells reduces the apparent number of insulin receptors in a relatively constant way by less than 8% a week after 10 days of storage. At the same time the dissociation constants of the insulin-receptor complex increase rapidly. Thus the use of a preparation must be limited to controlling the determination of the insulin binding sites of erythrocytes, and not to the measurement of the affinities of the receptors. When mono-¹²⁵I-Tyr-A14-insulin gets old, a slow decrease in the insulin binding sites can be measured, but the dissociation constants of the insulin receptor complex are not affected.

Key Words:

• erythrocyte
• insulin receptor
• ¹²⁵I-insulin
• quality control