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Effects of lovastatin treatment on red blood cell and platelet cation transport
A B Weder1, C Serr, B A Torretti
1University of Michigan Medical Center, Department of Internal Medicine, Ann Arbor 48109-0356.
Insights
Lowering high cholesterol with lovastatin did not affect red blood cell ion transport but did reduce platelet sodium-proton exchange, suggesting a link between cholesterol levels and hypertension markers.
Area of Science:
- Cardiovascular Science
- Membrane Transport Physiology
- Pharmacology
Background:
- Hypercholesterolemia often coexists with hypertension.
- Altered red blood cell membrane lipid composition may affect ion transport, potentially confounding hypertension research.
- Investigating the impact of lipid-lowering on membrane transport is crucial for understanding hypertension markers.
Purpose of the Study:
- To determine if altering plasma lipids affects red blood cell (RBC) membrane transport.
- To investigate the effects of lovastatin on RBC lithium-sodium countertransport, sodium-potassium-chloride cotransport, and sodium/water content.
- To assess lovastatin's impact on platelet amiloride-sensitive volume responsiveness as a measure of sodium-proton exchange.
Main Methods:
- A 24-week, randomized, double-blind, placebo-controlled trial.
- Administration of lovastatin to lower plasma cholesterol levels.
- Measurement of RBC ion transport (lithium-sodium countertransport, sodium-potassium-chloride cotransport, sodium/water content) and platelet sodium-proton exchange.
Main Results:
- Lovastatin significantly reduced total and LDL cholesterol, and increased HDL cholesterol.
- No significant alterations were observed in RBC lithium-sodium countertransport or sodium-potassium-chloride cotransport.
- RBC sodium content decreased significantly, likely due to increased Na-K pump activity.
- Platelet amiloride-sensitive responses were significantly depressed, indicating suppressed platelet sodium-proton exchange.
Conclusions:
- Lowering plasma cholesterol with lovastatin impacts platelet sodium-proton exchange but not major RBC ion transport systems.
- These findings suggest that plasma cholesterol levels may influence membrane transport markers relevant to hypertension.
- Further research is needed to clarify the role of lipid composition in hypertension-related membrane abnormalities.
Abstract:
Hypercholesterolemia frequently accompanies hypertension, and it has been suggested that by affecting membrane lipid composition, hypercholesterolemia may cause or accentuate abnormalities in several red blood cell transports associated with hypertension. Such an effect might obfuscate the relation of membrane markers to hypertension and decrease their usefulness in genetic studies of the heritable basis of hypertension. To determine if changing plasma lipids affects membrane transport, we studied the effects of the cholesterol-lowering agent lovastatin on red blood cell lithium-sodium countertransport and sodium-potassium-chloride cotransport, red blood cell sodium and water content, and platelet amiloride-sensitive volume responsiveness to cytoplasmic acidification, an indirect measure of sodium-proton exchange that has been proposed as a new membrane marker for hypertension. In a 24-week, placebo-controlled, double-blinded, randomized trial, lovastatin significantly lowered total and low density lipoprotein cholesterol and raised high density lipoprotein cholesterol. Red blood cell lithium-sodium countertransport and sodium-potassium-chloride cotransport were not significantly altered. Red blood cell sodium content decreased significantly in the lovastatin-treated group, probably as a result of an increase in red blood cell sodium-potassium pump activity. Platelet amiloride-sensitive responses to cytoplasmic acidification were significantly depressed by lovastatin treatment, suggesting that lowering plasma cholesterol may suppress platelet sodium-proton exchange. It has been hypothesized that the hyperlipidemias frequently observed in essential hypertensive patients may alter membrane lipid composition and affect membrane cation transport activities.(ABSTRACT TRUNCATED AT 250 WORDS)