The time for reflection: a luxury of the past

We have examined the in vitro effect of glucocorticoid and nonglucocorticoid steroids on the transport of [3-(14)C]alpha aminoisobutyric acid (AIB) in lymphocytes from patients with chronic lymphocytic leukemia (CLL), and myeloblasts from patients with acute granulocytic leukemia (AGL). AIB uptake by CLL lymphocytes was markedly inhibited at 1.0 muM (52+/-2.1%) and slightly inhibited at 0.1 muM (17+/-3.0%) cortisol. A similar degree of inhibition developed at 50-fold lower concentrations of dexamethasone, indicating that the effect of these steroids on AIB accumulation parallels their glucocorticoid activity in vivo. In contrast, minimal or no inhibition was observed with steroids devoid of glucocorticoid activity (progesterone, testosterone, cortisone). 11-deoxycortisol, a nonglucocorticoid known to impede the binding of cortisol to cellular receptors in animal lymphocytes, failed to inhibit AIB uptake by CLL lymphocytes appreciably, but reduced the effect of cortisol to a statistically significant degree. Hence, cortisol-induced inhibition of AIB transport in CLL lymphocytes is related to its glucocorticoid activity and appears to require initial interaction with glucocorticoid-specific cellular receptors. In contrast, 1.0 muM cortisol enhanced the accumulation of AIB in AGL myeloblasts from each of five patients studied (mean = 19%, range 7-43%). Neither cortisone nor 11-deoxycortisol stimulated AIB uptake, and cortisol-mediated stimulation was not seen during simultaneous treatment with 11-deoxycortisol, suggesting that this effect of cortisol also represents a specific glucocorticoid effect. The divergent effects of cortisol on amino acid transport in CLL lymphocytes and AGL myeloblasts may explain, in part, the contrasting clinical effects of glucocorticoids administered to patients with these lymphoid and granulocytic hematopoietic malignancies.