[Decrease in the regulatory capacity of the calcium pump in a subgroup of essential hypertensive patients].
We developed a new flux technique, useful for the clinical investigation of Ca2+ pump kinetics in intact erythrocytes. The initial rate of Sr2+ efflux (mediated by the Ca2+ pump) was studied as a function of steady state erythrocyte Sr2+ and Ca2+ contents in 22 Caucasian essential hypertensive patients (8 females, 14 males), aged 39-66 years (mean 51) and compared with 20 normotensive control subjects (10 females, 10 males), aged 22-57 years (mean 41). Kinetic analysis of the data (by using a two-sites model) allowed the determination of the apparent dissociation constants for internal Ca2+ (KCa) and for internal Sr2+ (KSr) and the maximal rate of Sr2+ efflux (Vmax). Mean values of these kinetic parameters were slightly increased in the hypertensive population. However, only the increase in KCa reached statistical significance (73 +/- 7 vs 55 +/- 3 mumol/l.cells, Mann-Whitney U test; p = 0.042). Individual analysis of the data showed that 6 essential hypertensives had a KCa higher than the upper normal limit (95 p. 100 confidence limit) of the normotensive group. In addition, mean values of Vmax and KSr were also significantly higher in these six essential hypertensives. In conclusion, about 25 p. 100 of the hypertensive patients had a decreased apparent affinity of the Ca2+ pump for internal Ca2+, which appears to be compensated (in the basal state) by an increased maximal pump rate. A similar abnormality in vascular smooth muscle cells may induce increased contractility by transitory cell Ca2+ retention after the opening of Ca2+ channels.
de la Sierra
A
A
Inserm U 7, hôpital Necker, Paris.
Hannaert
P
P
Senn
N
N
Ollivier
J P
JP
Garay
R
R
D000328:Adult; D000368:Aged; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000378:metabolism*; D008297:Male; D008875:Middle Aged
D015220:Calcium Channels; D002118:Calcium
Diminution de la capacité régulatrice de la pompe à calcium dans un sous-groupe de malades hypertendus essentiels.