The role of endogenous Na+, K(+)-adenosine triphosphatase inhibitory factor in the regulation of membrane fluidity of erythrocytes in essential hypertension.
OBJECTIVE
To investigate the regulatory mechanisms of membrane functions in hypertension, we examined the relationship between endogenous Na+, K(+)-adenosine triphosphatase (ATPase) inhibitor (digitalis-like factor; DLF) and erythrocyte membrane fluidity in essential hypertension by means of an electron spin resonance (ESR) and spin labelling methods.


METHODS
Erythrocytes were obtained from patients with essential hypertension and normotensive subjects, and the ESR spectra for a fatty acid spin label agent (5-nitroxide stearate) incorporated into the erythrocyte membranes were studied. The DLF content in plasma was expressed as the inhibitory potency of dog kidney Na+, K(+)-ATPase activity in vitro.


RESULTS
The values of outer hyperfine splitting and of order parameter in ESR spectra were significantly higher in hypertensive patients than in normotensive subjects. This finding shows that the erythrocyte membrane fluidity may be decreased in essential hypertension. The level of plasma DLF content was greater in hypertensive patients than in normotensive subjects and was significantly correlated with the decrease in erythrocyte membrane fluidity.


CONCLUSIONS
These results suggest that the decrease in erythrocyte membrane fluidity may be partially dependent upon the increased plasma DLF content.
Tsuda
K
K
Department of Medicine, Wakayama Medical College, Japan.
Shima
H
H
Takeda
J
J
Kimura
K
K
Nishio
I
I
Masuyama
Y
Y
D001798:Blood Proteins / Q000502:physiology*; D002298:Cardenolides; D004077:Digoxin; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood / Q000378:metabolism*; D008297:Male; D008560:Membrane Fluidity / Q000502:physiology*; D008875:Middle Aged; D012503:Saponins; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors*; D013113:Spin Labels
D001798:Blood Proteins; D002298:Cardenolides; D012503:Saponins; D013113:Spin Labels; C034504:digoxin-like factors; D004077:Digoxin; D000254:Sodium-Potassium-Exchanging ATPase