Oral calcium supplementation ambulatory blood pressure and relation to changes in intracellular ions and sodium-hydrogen exchange.
BACKGROUND
Calcium (Ca2+) supplementation has been shown paradoxically to reduce intracellular Ca2+ and induce vascular relaxation. The aim of the study was to assess 24-h blood pressure (BP) change after Ca2+ supplementation and to investigate its relation to changes in intracellular ions and the activity of the first isoform of sodium-hydrogen exchange (NHE-1) in subjects with hypertension and type 2 diabetes.


METHODS
This parallel, randomized controlled, single-blinded trial, consisted of 31 patients with type 2 diabetes, and hypertension who were allocated to receive 1,500 mg of Ca2+ per day (n = 15) or no treatment (n = 16) for 8 weeks.


RESULTS
In the Ca2+ group a decrease of 1.7 +/- 2.7 mm Hg (mean +/- SE) P = 0.52 for mean 24-h systolic BP (SBP) and 2.1 +/- 1.5 mm Hg, P = 0.19 for mean 24-h diastolic BP (DBP) was recorded. Whereas in the control group an increase of 1.4 +/- 2.7 mm Hg, P = 0.59 for mean 24-h SBP and 1.2 +/- 2.8 mm Hg, P = 0.83 for mean 24-h DBP was observed. Intraplatelet Ca2+ decreased whereas intraplatelet magnesium (Mg2+) and erythrocyte K+ increased in the intervention group. Change in mean 24-h SBP in the pooled group correlated with both change in intraplatelet Ca2+ (r = 0.49, P < 0.05) and NHE-1 activity (r = 0.6, P < 0.001). The contribution of intraplatelet Ca2+ was attenuated when both parameters were entered in a multivariate regression model.


CONCLUSIONS
The present study shows a weak, statistically nonsignificant trend towards association of Ca2+ supplementation on 24-h BP in hypertensive subjects with type 2 diabetes. However, our results indicated an interrelation of [Ca2+]i levels and NHE-1 activity on BP in patients with hypertension and type 2 diabetes.
Pikilidou
Maria I
MI
1st Department of Internal Medicine, Aristotle University of Thessaloniki, AHEPA Hospital, Thessaloniki, Greece. m_pikilidou@yahoo.com
Befani
Christina D
CD
Sarafidis
Pantelis A
PA
Nilsson
Peter M
PM
Koliakos
George G
GG
Tziolas
Ioannis M
IM
Kazakos
Kiriakos A
KA
Yovos
John G
JG
Lasaridis
Anastasios N
AN
D000368:Aged; D001794:Blood Pressure / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D002136:Calcium, Dietary / Q000627:therapeutic use*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D006973:Hypertension / Q000188:drug therapy*; D008274:Magnesium / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D011188:Potassium / Q000378:metabolism; D016037:Single-Blind Method; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000097:blood*
D002136:Calcium, Dietary; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium