Dexamethasone suppression test: corticosteroid receptors regulation in mononuclear leukocytes of young and aged subjects.

The dexamethasone suppression test (DST) is considered an indicator of the function of the adrenal pituitary axis. The effect of the steroid is mediated by its binding to corticosteroid receptors. We previously suggested that the measurement of corticosteroid receptors in lymphocytes is an index of an analogous pattern in brain. In the present study, corticosteroid Type I and Type II receptors in mononuclear leukocytes were measured in 10 elderly subjects and in 9 young adults, before and after overnight DST (1 mg). Receptors were measured by radioreceptor assay. In all the subjects, dexamethasone was able to suppress plasma cortisol. The number of Type I and Type II receptors before the test was lower in elderly subjects than in adults. In the control group, dexamethasone produced a significant depression of Type I receptors (from 267 +/- 72 to 169 +/- 71 receptors per cell), which can be interpreted as a primary involvement of Type I receptors in the response to dexamethasone; Type II receptors decreased in half the subjects (from 2849 +/- 703 to 2345 +/- 569 receptors per cell). In elderly healthy subjects, Type II receptors were also significantly decreased (from 1796 +/- 671 to 720 +/- 345). We suggest that in young subjects Type II receptors are initially up-regulated by dexamethasone, and then down-regulated, while in aged subjects an up-regulation cannot be achieved, as suggested by the higher values of plasma cortisol usually found in aging subjects.