Nitric oxide is a determinant of membrane fluidity of erythrocytes in postmenopausal women: an electron paramagnetic resonance investigation

Abstract

In the present study, to determine a possible role of nitric oxide (NO) in the regulation of membrane functions, we examined the relationship between plasma NO level and membrane fluidity of erythrocytes in postmenopausal women. We evaluated the membrane fluidity of erythrocytes obtained from hypertensive and normotensive postmenopausal women by means of an electron paramagnetic resonance (EPR) and spin labeling method. The EPR study revealed that the order parameter (S) for 5-nitroxide stearate in erythrocyte membranes was significantly greater in hypertensive postmenopausal women than in normotensive postmenopausal women. The finding indicated that the membrane fluidity of erythrocytes was decreased in hypertensive postmenopausal women compared with normotensive postmenopausal women. The plasma level of the NO metabolites (nitrite and nitrate) while fasting was significantly lower in hypertensive postmenopausal women than in normotensive postmenopausal women. In addition, the order parameter (S) in the EPR spectra of erythrocyte membranes was inversely correlated with the plasma NO metabolite level, which indicated that the lower membrane fluidity of erythrocytes was associated with the lower plasma NO level in postmenopausal women. These results are consistent with the hypothesis that NO may have a crucial role in the regulation of membrane fluidity of erythrocytes in postmenopausal women.

Oxidative Stress and Membrane Fluidity of Red Blood Cells in Hypertensive and Normotensive Men An Electron Spin Resonance Investigation

“…The RBC preparation and ESR measurement procedures have been described previously. [9][10][11][12][13] We evaluated the values of outer and inner hyperfine splitting (2T' ￨￨ and 2T' ⏊ in G, respectively) in the ESR spectra for the spin label agent (5-nitroxide stearate, Aldrich Co. Ltd., Milwaukee, Wisconsin, USA) and calculated the order parameter (S). [9][10][11][12][13] The greater the value of the order parameter (S) was, the lower the membrane fluidity of RBCs.…”

“…[9][10][11][12][13] We evaluated the values of outer and inner hyperfine splitting (2T' ￨￨ and 2T' ⏊ in G, respectively) in the ESR spectra for the spin label agent (5-nitroxide stearate, Aldrich Co. Ltd., Milwaukee, Wisconsin, USA) and calculated the order parameter (S). [9][10][11][12][13] The greater the value of the order parameter (S) was, the lower the membrane fluidity of RBCs. [9][10][11][12][13] Plasma 8-Iso-PG F2α levels were determined by using an enzyme immunoassay (Cayman Chemicals Co., Ann Arbor, Michigan, USA).…”

“…[9][10][11][12][13] The greater the value of the order parameter (S) was, the lower the membrane fluidity of RBCs. [9][10][11][12][13] Plasma 8-Iso-PG F2α levels were determined by using an enzyme immunoassay (Cayman Chemicals Co., Ann Arbor, Michigan, USA). 5,6) The plasma levels of NOmetabolites (nitrite and nitrate) were measured according to the method described previously.…”

“…8,9) Using the ESR method, we have been performing a series of experiments regarding the membrane fluidity in subjects with essential hypertension. [9][10][11][12][13] The results suggest that the membrane fluidity of red blood cells (RBCs) was significantly lower in hypertensive subjects than in normotensive subjects, indicating that the cell membranes were stiffer and less fluid in essential hypertension. [9][10][11][12][13] Because the deformability of RBCs may be highly dependent on the membrane fluidity, 8) the reduction in membrane fluidity of RBCs could cause a disturbance in the blood rheologic behavior and in the microcirculation, which might contribute to the pathophysiology of hypertension and other circulatory disorders.…”

“…[9][10][11][12][13] The results suggest that the membrane fluidity of red blood cells (RBCs) was significantly lower in hypertensive subjects than in normotensive subjects, indicating that the cell membranes were stiffer and less fluid in essential hypertension. [9][10][11][12][13] Because the deformability of RBCs may be highly dependent on the membrane fluidity, 8) the reduction in membrane fluidity of RBCs could cause a disturbance in the blood rheologic behavior and in the microcirculation, which might contribute to the pathophysiology of hypertension and other circulatory disorders. 8,9) In the present study, in order to assess the role of oxidative stress in the regulation of membrane function in hypertension, we investigated the relationships between plasma 8-Iso-PG F2α and membrane fluidity of red blood cells (RBCs) in hypertensive and normotensive men.…”