[Calcium pump changes in patients with essential arterial hypertension]

Transmembrane Ca2+ fluxes are mediated, at least in part, by the Ca(2+)-dependent ATPase. Thus, genetic or acquired abnormalities of this pump could explain the increase in free cytosolic Ca2+ content that has been observed in essential hypertensive patients.

We carried out a kinetic study of the Ca2+ pump in intact erythrocytes from 49 essential hypertensive patients and 27 normotensive healthy persons. We used Sr2+ as a calcium analogue to measure Ca2+ fluxes dependent of the Ca2+ pump. The intracellular concentrations of Sr2+ and Ca2+ were modified using the A-23187 ionophore in a Ringer isotonic solution.

Hypertensive patients showed a significant increase of the maximal efflux rate for Sr2+ (Vmax) with respect to controls (6.6 [2.3] vs 5.2 [1.6] mmol/l cel/h; p = 0.006). Mean values of apparent dissociation constants for intracellular Ca2+ (KCa) were also increased in essential hypertensives (80.36 [53.46] vs 55.25 [15.13] mumol/l cel; p = 0.06). A significant correlation between Vmax and age (r = 0.342; p = 0.016), and serum creatinine (r = 0.446; p = 0.001) was observed. The KCa only correlated with serum creatinine (r = 0.402; p = 0.004). Using the KCa confidence interval of 99% as the higher normal limit, patients were segregated into two subgroups depending on normal KCa values (33 patients, 67.3%) or increased KCa values (16 patients, 32.6%). Age (50.8 [13.5] vs 43 [10.2] years; p = 0.02), serum creatinine (1.13 [0.17] vs 0.95 [0.17] mg/dl; p = 0.001) and serum uric acid (7.27 [3.32] vs 6.14 [1.49] mg/dl; p = 0.04) were higher in patients with increased KCa. Finally, patients with increased KCa also showed increased values of Vmax (9.13 [2.02] vs 5.38 [12.81] mmol/l cel/h; p < 0.0001).

Essential hypertensive patients are heterogeneous regarding ion transport abnormalities, only affecting subgroups of hypertensive patients. We have observed abnormalities of the Ca(2+)-dependent ATPase in 33% of essential hypertensive patients. These patients are older and tend to exhibit higher values of serum creatinine and uric acid.