Erythrocyte Na(+)-Li+ countertransport in essential hypertension: correlation with membrane lipids levels.

OBJECTIVE: To examine whether Na(+)-Li+ countertransport (SLC) activity is linked to erythrocyte membrane lipid content.
DESIGN: An observational case-control study. The maximal efflux rate of SLC, plasma cholesterol, triglycerides, phospholipids, low- and high-density lipoprotein cholesterol levels and the erythrocyte membrane cholesterol, phospholipids and fatty acids contents were determined both in fasting normolipaemic normotensive subjects and in hypertensive patients.
METHODS: The Li(+)-stimulated Na+ efflux was measured in Li(+)-preloaded erythrocytes. Membrane cholesterol and phospholipids levels were determined by the latroscan technique. Membrane fatty acids were identificated by gas chromatography. Several derived indices were also obtained.
RESULTS: Erythrocyte membranes of hypertensive patients showed an increase in cholesterol: phospholipid ratio and a decrease in the total amount of polyunsaturated fatty acids, mainly at the expense of arachidonic acid and docosatetraenoic acid. SLC activity was higher in hypertensive patients and correlated positively with the plasma triglycerides level and negatively with the ratio of C20:4 to C20:3.
CONCLUSION: Our data from untreated normolipaemic hypertensive patients show that a higher SLC activity was accompanied by parameters that indicate a lower membrane fluidity.