Plasma membrane fluidity and polarity of polymorphonuclear leukocytes fromchildren with type I diabetes mellitus

Polymorphonuclear leukocytes (PMN) from diabetic subjects have been found t o be abnormal in various functional activities. These activities are mediat ed by the plasma membrane. This study was designed to evaluate plasma membr ane fluidity and polarity in children with type I diabetes mellitus using f luorescence spectroscopy. FMN membrane fluidity and polarity were assessed in a group of 32 diabetic children. Membrane fluidity was investigated. by measuring steady-state fluorescence anisotropy and fluorescence decay of 1- [4-trimethylammonium-phenyl]-6-phenyl- 1,3,5-hexatriene (TMA-DPH), whereas membrane polarity was studied by measuring the steady-state fluorescence em ission and excitation spectra of 2-dimethylaminol[6-lauroyl]-naphthalene (L aurdan). TMA-DPH and Laurdan are known to be incorporated at the hydrophobi c-hydrophilic interface of the bilayer. Our data show a significant increas e in steady-state fluorescence anisotropy in diabetic PMN that reflects a d ecrease in membrane fluidity, and a decrease in TMA-DPH lifetime distributi on indicating a decrease in membrane heterogeneity. Laurdan shows a blue sh ift of the fluorescence emission and a red shift of the excitation spectra in diabetic PMN with respect to the control group, indicating a decrease in membrane polarity. The results demonstrate a decrease in the phospholipid order at the membrane surface and a decrease in membrane polarity in diabet ic PMN. These alterations in the physico-chemical properties of the plasma membrane could be the basis of the modifications in functional activities o f PMN. The changes in the plasma membrane of PMN could be the result of met abolic and chemical modification associated with type I diabetes. (C) 2000 Elsevier Science Inc.