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Diuretics and cation transport in hypertensive blacks
1VA Lakeside Medical Center, Chicago, IL 60611.
Insights
Thiazide diuretics effectively treat hypertension in Black individuals by stimulating the sodium-potassium (Na,K) pump. This action may help correct volume expansion and lower blood pressure.
Area of Science:
- Cardiology
- Nephrology
- Pharmacology
Background:
- Thiazide diuretics are highly effective for hypertension management in Black populations.
- Hypertensive Black individuals often exhibit characteristics of volume expansion.
- Inhibition of the sodium-potassium (Na,K) pump is observed in leukocytes and erythrocytes of hypertensive Black individuals.
Purpose of the Study:
- To investigate the mechanism by which thiazide diuretics improve hypertension in Black patients.
- To determine if thiazide diuretics stimulate the Na,K pump in hypertensive Black individuals.
Main Methods:
- A study was conducted on 13 Black men with essential hypertension.
- Participants received hydrochlorothiazide (50 mg/day) for 7 days.
- Measurements included sodium efflux and Na,K-adenosine triphosphatase (Na,K-ATPase) activity in erythrocytes.
Main Results:
- Sodium efflux and erythrocyte Na,K-ATPase activity significantly increased after hydrochlorothiazide treatment.
- These findings support the hypothesis that thiazide diuretics stimulate the Na,K pump.
- Potential for reduced intracellular calcium in vascular smooth muscle was noted.
Conclusions:
- Thiazide diuretics may exert their antihypertensive effects in Black individuals by stimulating the Na,K pump.
- This stimulation could counteract volume expansion and contribute to blood pressure reduction.
- Further research may explore the link between diuretic therapy, Na,K pump activity, and vascular smooth muscle calcium levels.
Abstract:
Thiazide diuretics are particularly efficacious in the treatment of hypertension in blacks. A number of observations suggest that many hypertensive blacks have features consistent with a status of "corrected" volume expansion. Our studies, as well as those of other investigators, show that the Na,K pump is inhibited in leucocytes and erythrocytes of blacks with essential hypertension. This observation is also consistent with the concept of volume expansion in hypertensive blacks, since the Na,K pump is inhibited in many forms of experimental volume expansion, including the administration of salt in normal humans. We postulate that the efficacy of thiazide diuretics may be related to their ability to stimulate the Na,K pump. We present data obtained in 13 black hypertensive men in whom Na efflux, and Na,K-ATPase in the erythrocyte rose significantly after 7 days of treatment with hydrochlorothiazide, 50 mg/day. Diuretic therapy may indirectly result in reduced intracellular calcium in the vascular smooth muscle.