CELL CYCLE-SPECIFIC EFFECTS OF GLUCOCORTICOIDS ON PHYTO-HEMAGGLUTININ-STIMULATED LYMPHOCYTES

  • 1 January 1980
    • journal article
    • research article
    • Vol. 39  (2) , 503-509
Abstract
Effects of steroid hormones and colchicine on the response of pig lymphocytes to phytohemagglutinin (PHA) were assessed by measurement of [6-3H]thymidine incorporation. At steroid concentrations of 1 .mu.M and below, only glucocorticoids and progesterone inhibited PHA-stimulated [6-3H]thymidine incorporation but at 100 .mu.M inhibition was also produced by estrogens, androgens and physiologically inactive steroids. Measurement of [6-3H]thymidine incorporation 18-24 h, 6-12 h or 0-6 h after the delayed addition of the synthetic glucocorticoid, dexamethasone, to PHA-stimulated lymphocytes revealed a succession of alternating phases of sensitivity and insensitivity to the effects of the steroid which suggested that it was acting, perhaps indirectly, in a cell cycle stage-specific manner to arrest the progression of activated lymphocytes from G1 to S. Similar effects were observed with colchicine, but 100 .mu.M 11-epicortisol inhibited [6-3H]thymidine incorporation in a non-cycle-specific manner. Glucocorticoid receptor levels in pig lymphocytes were increased 2.5-fold within 24 h of PHA stimulation.