Glucocorticoid effects on membrane lipid mobility during differentiation of murine B lymphocytes.

The lateral motion of membrane lipids on lipopolysaccharide-stimulated murine B lymphocytes was measured using photobleaching recovery techniques. The mobility of the phospholipid analog 3,3'-dioctadecylindocarbocyanine iodide (DiI) was measured at 37 degrees C on B lymphocytes 48 h after stimulation by various concentrations of lipopolysaccharide. DiI mobility on lymphoblasts from cultures stimulated with 10 micrograms/ml lipopolysaccharide was reduced 50% compared with unstimulated, small B cells. However, both lower and higher lipopolysaccharide concentrations caused some decrease in lipid mobility. Lipid mobility was measured on B cells stimulated with 10 micrograms/ml lipopolysaccharide at zero time, on lymphoblasts at 18, 24, 48 and 72 h, and on immunoglobulin (Ig) -secreting lymphocytes at 96 h. The diffusion coefficient of DiI on both control and lipopolysaccharide-treated cells at zero time is 6.3 X 10(-9) cm2 X s-1. This value remains unchanged for unstimulated cells over 72 h. Lipid mobility of lipopolysaccharide-activated lymphoblasts decreased during incubation with lipopolysaccharide to 5.0, 3.4, 2.8 and 2.4 X 10(-9) cm2 X s-1 after 18, 24, 48 and 72 h, respectively. DiI mobility on immunoglobulin (Ig) -secreting lymphocytes identified at the foci of Protein A-coated sheep red blood cells plaques is 8.6 X 10(-9) cm2 X s-1, a value similar to that of unstimulated B cells. The effect of introducing various concentrations of a synthetic glucocorticoid, triamcinolone acetonide (TA), to 48 h lipopolysaccharide-stimulated cells for 6 h was examined. Maximal TA effect was observed at a concentration of 10(-7) M, which caused an increase in lipid mobility to 7.5 X 10(-9) cm2 X s-1. Exposing resting B cells (t = 0) or lymphoblasts (t = 24, 48 or 72 h) to TA for 3 h had no effect on lipid mobility. Treatment for 6 h with 10(-7) MTA increased DiI diffusion to 12.6, 9.9, 7.5 and 6.8 X 10(-9) cm2 X s-1 on control cells and on 24, 48 and 72 h lipopolysaccharide-activated lymphoblasts, respectively. A longer incubation of 12 h with 10(-7) MTA caused no further change in lipid lateral diffusion. The response was glucocorticoid-specific. In lymphoblasts (48 h) incubated an additional 6 h with 10(-7) MTA and a 100-fold excess of cortexolone or progesterone, the increase in lipid mobility was substantively blocked; estradiol and testosterone had no effect on lipid lateral diffusion.(ABSTRACT TRUNCATED AT 400 WORDS)