Effect of dietary sodium on platelet alpha 2-adrenergic receptors in essential hypertension.

Abstract

SUMMARY To study the aggregation, adhesion, and specific binding of an a 2 -antagonist, [ 3 H]rauwolscine, to the platelet membrane fractions, platelets were obtained from 30 patients with essential hypertension and nine normotensive subjects fed a high sodium diet (NaCl, 16-18 g/day) for 7 days and thereafter a low sodium diet (NaCl, 1-3 g/day) for 7 days. The patients with essential hypertension were classified as either salt responders (all those who had > 7% decrease in mean arterial pressure from the high to low sodium period) or salt nonresponders (all others). In salt responders, the number of a 2 -adrenergic receptors on platelet membrane fraction was increased from 523.4 ± 55.4 fmol/mg of protein in the high sodium period to 669.4 ± 84.0 fmol/mg of protein in the low sodium period (p < 0.01), whereas it did not change in salt nonresponders. In contrast, the epinephrine-induced platelet aggregation through a 2 -adrenergic receptors was decreased in nonresponders, from 47.3 ± 7.4% in the high sodium period to 24.5 ± 9.3% in the low sodium period (p < 0.05), while it did not change in responders. No significant change in the number of c* 2 -adrenergic receptors or epinephrine-induced platelet aggregation was observed in the normotensive subjects.

The sensitivity of human blood platelets to the aggregating agent ADP during different dietary sodium intakes in healthy men

“…The aggregation results in this study agree with those from previous reports [1][2][3] in showing that there is a direct relation between sodium intake and the extent of platelet aggregation measured in vitro. A rise in sodium intake increased the sensitivity of the platelets to ADR an important factor which has been related to the incidence of sudden death by myocardial infarction [20].…”

Harmful effects of dietary salt in addition to hypertension

“…In those in whom there was a rise in blood pressure, platelet aggregation also rose as did the number of ␣-2 adrenergic receptors. 55 …”

Peripheral adrenergic receptors in hypertension.

“…Moreover, increased dietary salt intake reduces the plasma levels of catecholamines. 72 Thus, in hypertensive subjects /3-adrenergic receptor desensitization occurs in spite of reduced sympathetic drive. The molecular mechanisms of this desensitization remain to be defined.…”

“…57 Similarly, a high sodium diet decreased plasma catecholamines and increased platelet a 2 -adrenergic receptors in normotensive Caucasian subjects. 84 In hypertensive Japanese subjects, however, a high sodium diet reduced platelet a 2 -adrenergic receptors 72 ; in this study a separate analysis was performed of those patients who responded with increases in blood pressure to increased sodium intake and those who did not. "Sodium-responders" on a high sodium diet had 35% lower plasma norepinephrine concentrations compared with the low sodium phase; nonresponders, however, decreased their plasma norepinephrine by 60%.…”