T. Tanyalcin et al., ERYTHROCYTE NA-ATPASE ACTIVITY DOES NOT PREDICT THERAPEUTIC RESPONSE TO CALCIUM-ANTAGONISTS IN ESSENTIAL-HYPERTENSION(,K+), Clinical chemistry, 40(8), 1994, pp. 1532-1536
We investigated whether pre- and posttreatment analysis of erythrocyte
membrane Na+,K+-ATPase (EC 3.6.1.37) activity would be a useful marke
r for screening hypertensive patients to determine who might benefit f
rom treatment with calcium antagonists. Erythrocyte Na+,K+-ATPase acti
vity and sodium and potassium (ENa, EK) contents were determined in co
ntrols and in patients with untreated essential hypertension before an
d after 4 weeks of treatment with nitrendipine. Na+,K+-ATPase activity
was significantly (P < 0.0001) less in untreated hypertensive patient
s (n = 15; 104.60 +/- 29.37 nmol of phosphate produced per milligram o
f protein per hour) than in controls (n = 15, 171.87 +/- 34.42). After
4 weeks of nitrendipine treatment Na+,K+-ATPase activity was greater
than in the pretreatment group: 158.13 +/- 26.80 (P < 0.001). Pretreat
ment ENa contents (22.34 +/- 4.77 mmol/L) were significantly (P < 0.00
01) higher than in the normotensive group (13.14 +/- 3.32 mmol/L), but
there was no significant difference between the controls and the post
treatment group (14.84 +/- 3.49 mmol/L). The control and pretreatment
groups showed negative correlations between enzyme activity and systol
ic/diastolic blood pressure (P < 0.0001). The control and the posttrea
tment groups showed an inverse correlation between enzyme activity and
ENa contents: r = -0.608 (P < 0.05) and r = -0.724 (P < 0.001), respe
ctively. Although Na+,K+-ATPase is restored in hypertensive patients r
eceiving nitrendipine treatment, relative changes in enzyme activity i
n relation to relative reduction in blood pressure response to treatme
nt were not correlated.