u-25166 and hydrocortisone-acetate

We have used spin labeling, fluorescence polarization, and chemical analysis to characterize membrane properties of thymocytes from mice treated with immunomodulatory drugs. The number of thymocytes was reduced 90-95% by treatment of 6-9 week old mice with hydrocortisone acetate (HCA) or methylprednisolone (both 125 mg/kg) or with cyclophosphamide (250 mg/kg). Electron spin resonance (esr) examination of thymocytes labeled with 5-nitroxyl stearic acid indicated that the membranes of cells remaining after treatment with any of these drugs were more rigid than those from saline-treated controls. The total cholesterol/phospholipid (C/PL) molar ratio of the HCA-resistant thymocytes was twice that of the control mice. Treatment of mice with other immunomodulatory drugs, cyclophosphamide, cytosine arabinoside (Ara-C), 2-amino-5-bromo-6-phenyl-4-(3H)-pyrimidinone (ABPP) and 15(S)-methyl prostaglandin E1 (15(S)-methyl PGE1), also altered the C/PL ratio in thymocytes and, in some cases, in spleen cells. Fluorescence polarization measurements of thymocytes labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH) did not reveal the differences between cells from HCA-and saline-treated mice that were detected by spin labeling and chemical analysis. Our results indicate that the greater rigidity detected by spin labeling of hydrocortisone-resistant thymocytes may be due, at least in part, to greater membrane cholesterol content. Of the methods employed, chemical analysis was the most sensitive in revealing drug-induced alterations in thymocyte populations.

Topics: Alprostadil; Animals; Cell Membrane; Cholesterol; Cyclophosphamide; Cytarabine; Electron Spin Resonance Spectroscopy; Female; Hydrocortisone; Immunosuppressive Agents; Male; Methylprednisolone; Mice; Mice, Inbred AKR; Mice, Inbred C57BL; Mice, Inbred CBA; Prostaglandins E, Synthetic; Pyrimidines; Spectrometry, Fluorescence; Spleen; Thymus Gland