P-688: Progesterone improves membrane function of erythrocytes by the nitric oxide-dependent mechanism -an electron paramagnetic resonance investigation

• Published in: American journal of hypertension Vol. 14; no. S1; p. 260A
• Main Authors: Tsuda, K., Tsuda, S., Nishio, I., Masuyama, Y.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.04.2001
• Subjects: Membrane fluidity; Nitric oxide; Progesterone
• ISSN: 0895-7061; 1941-7225
• DOI: 10.1016/S0895-7061(01)02036-2

It has been shown that hormone replacement therapy with estrogen and progesterone provides protection against the development of hypertension, arteriosclerosis and other cardiovascular diseases. However, the precise mechanism underlying its benefits is unclear. Our recent study demostrated that estrogen improved membrane microviscosity of erythrocytes. In the present study, we examined the effects of progesterone on membrane fluidity of erythrocytes in normotensive subjects by means of an electron paramagnetic resonance (EPR) and spinlabeling method. Progesterone significantly decreased the order parameter (S) for 5-nitroxide stearate (5-NS) and the peak height ratio (ho/h-1) for 16-NS obtained from EPR spectra of erythrocyte membranes (S: control 0.726±0.002, mean±SEM, n=31, prog 10-9mol/L 0.715±0.002, n=31, p<0.05, prog 10-8mol/L 0.710±0.002, n=31, P<0.05). The finding showed that progesterone increased the membrane fluidity of erythrocytes. The effect of progesterone was potentiated by the nitric oxide (NO)-donor, S-nitroso-N-acetylpenicillamine (SNAP) and a cGMP analog, 8-bromo-cGMP. In contrast, the progesterone-induced changes in membrane fluidity were significantly reversed in the presence of the NO synthase inhibitors, L-NG-nitroarginine-methyl-ester (L-NAME) and asymmetric dimethyl-L-arginine (ADMA). These results showed that progesterone increased membrane fluidity of erythrocytes and improved microviscosity of cell membranes by the NO-dependent mechanism. Furthermore, the data strongly suggest that progesterone might actively participate in the regulation of rheological behavior of erythrocytes and have a crucial role in the improvement of microcirculation.