Intracellular Na+ and Ca2+ Activities in Essential Hypertension

Abstract

The intracellular Na+ and Ca2+ activity andNa+ concentration were measured in erythrocytes of normotensive subjects, with and without a familial disposition to hypertension, in essential hypertensive patients with and without a family history of hypertension, and in patients with secondary hypertension. 2.In normotensive subjects without a genetic trait of hypertension intracellular Na+ activity and concentration were 7-00 L-1.38 mmol/l and 5.67 f 0.95 mmol/l respectively. The intracellular Ca2+ activity was 4.82 & 4-49 Nmol/l. In normotensive subjects with a familial hypertensive disposition intracellular Na+ activity and concentration were 9.74 f 1-43 mmol/l (P < 0.01) and 6.63 f 0.88 mmol/l (P < 0.05). Intracellular Ca2+ was 9-59 f 9.71 pmolll (P < 3. Essential hypertensive patients without a familial genetic trait had an elevated intracellular Na+ activity (8.35 f 2.08 mmol/l, P < 0.05).Intracellular Na+ concentration was 6.64 f 0-79 mmol/l (P < 0.05). The intracellular CaZ+ activity was markedly elevated to 25.33 f 19.03 pmol/l (P < 0.01). The essential hypertensive patients with a familial disposition had an elevated intracellular Na+ activity (17.19 f 4.37 mmol/l, P < 0-001) and Ca2+ activity (32.8 f 32.51 pmol/l, P < 0.01). The intracellular Na+ concentration was 6.25 f 1-23 mmol/l. 4.The results indicate that in essential hypertension intracellular Na+ activity is increased, particularly in patients with a familial disposition for hypertension. Intracellular Ca2+ is increased in essential hypertension whether or not there was a family disposition to hypertension.

Is calcium more important than sodium in the pathogenesis of essential hypertension?

“…78 -79 Since CaATPase is of fundamental importance in the final regulation of normal cytosolic calcium content, 79 -80 and if the RBC defects in calcium binding and CaATPase activation are reflective of a more generalized membrane-associated defect, then it follows that intracellular free calcium would be modestly elevated in platelets. 64 - 77 The possibility that a generalized defect does exist is supported by two additional observations: the intracellular calcium concentrations are elevated in RBCs of hypertensive persons, 81 and adipocytes obtained from hypertensive subjects exhibit similar alterations of intracellular calcium. 82 …”

Platelet Membrane and Calcium Control Abnormalities in Essential Hypertension

“…7 " 10 ' 14 " 16 A correlation between platelet [Ca 2+ ]i and blood pressure has also been estab- 10 perhaps due to a reduction in the num ber of Ca 2+ -binding sites (as opposed to an affinity alter ation). 18 Defective calcium binding has been proposed to favor depolarization with consequent activation of potential operated calcium channels.…”

Intracellular Free Ca⁺⁺ and Na⁺ in Primary Hypertension in Arterial Smooth Muscle and in Red Blood Cells

“…For measurements of intracellular Na* and Ca** activities, which are a measure of free Na* and Ca** concentrations, ion-selective electrodes were used [1], Studies in RBC were performed in 12 spon taneously hypertensive and 8 normotensive rats after washing the RBC in an isotonic solution (choline hydrogen tartrate and 5 mmol I NaCl) and then freezing to -18 °C and rcthawing for disrupting the membranes. From 7 spontaneously hypertensive and 9 normoten sive rats the abdominal aortas were excised and.…”