Transient effect of glucocorticoids on red blood cell insulin receptors

The effect of oral administration of dexamethasone or cortisone on circulating red blood cell (RBC) insulin receptors was evaluated in normal males before treatment and 24 h (day 1), 48 h (day 2) and 72 h (day 3) after the commencement of steroid administration. Dexamethasone induced a slight significant decrease of insulin binding (p less than 0.05) on days 1 and 3, whereas cortisone did not. Cortisone, on the other hand, produced transient reduction (i.e. insulin binding lower than mean -2 SD of control values) in six subjects out of eight on days 1, 2 or 3 varying from subject to subject. Binding impairment was due mainly to reduced receptor affinity, even if slight reduction of receptor concentration was detectable. Qualitatively the present data agree that impaired insulin binding is due mainly to reduced receptor affinity; however, the effect of steroids on RBC is not significant and persistent as that on monocytes. The less marked effect of dexamethasone and cortisone on RBC versus monocytes indicates that receptor modifications may be tissue specific.