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Objective: To study the effects of a high calcium intake in hypertensive patients by blood pressure monitoring., Design: In a randomized crossover study, patients were assigned to an 8-week calcium supplementation period and an 8-week control period. The subjects were given 25 mmol/day (1 g/day) of calcium as calcium carbonate during the intervention period., Setting: A hypertension clinic in a tertiary teaching hospital., Patients: Sixty untreated or treated hypertensive patients (35 men and 25 women, mean age 58 years) with office systolic/diastolic blood pressure > or = 140/90 mmHg., Main Outcome Measures: Office blood pressure, home blood pressure (last 7 days), and ambulatory 24 h blood pressure (every 30 min using TM-2421)., Results: The serum calcium concentration and urinary calcium excretion increased significantly with calcium supplementation. Office, home and 24 h blood pressure were lower in the calcium period than in the control period, although the differences were small (mean +/- SEM office blood pressure: 1.2+/-1.2/1.1+/-0.7 mmHg; home blood pressure: 1.9+/-0.7/1.3+/-0.6 mmHg; 24 h blood pressure: 1.2+/-0.8/0.9+/-0.5 mmHg,), and significant only for home systolic and diastolic blood pressures. The difference in home systolic blood pressure was inversely correlated with the level of home blood pressure in the control period and with the difference in urinary calcium. The difference in 24 h systolic blood pressure was positively correlated with the control level of urinary calcium. Age, sex, antihypertensive medication, drinking habit, sodium intake or order of treatment did not significantly influence the effects of calcium supplementation., Conclusions: An increase in calcium intake tends to lower office, home and ambulatory blood pressure in hypertensive patients. However, the antihypertensive effect is too small to support the general application of a high calcium intake in the treatment of hypertension.

Objective: To study the influence of seasons on blood pressure in ordinary circumstances., Design and Methods: We examined seasonal variations of home and 24 h ambulatory and office blood pressures in outpatients with essential hypertension. Office, home and ambulatory blood pressures of 50 outpatients with essential hypertension were recorded in 1993. The subjects were 26 women and 24 men, aged 59.3 +/- 1.1 years (mean +/- SEM). Office blood pressure was measured monthly by physicians. Home blood pressure was measured every day by the patients in the morning and evening. Ambulatory blood pressure was recorded every 30 min in summer and in winter. The order of ambulatory blood pressure monitoring was randomized. The daytime and night-time blood pressures were calculated according to the true waking and sleeping times of the individual patients., Results: Both office and home blood pressures showed significant seasonal variations. The winter-summer differences in office and home blood pressures were 4.7 +/- 1.3/ 3.3 +/- 0.9 and 5.9 +/- 1.1/2.7 +/- 0.6 mmHg, respectively. They were not influenced by the presence of antihypertensive agents. The winter-summer difference was also significant for daytime ambulatory blood pressure (3.5 +/- 1.4/ 2.5 +/- 0.8 mmHg), but not for night-time ambulatory blood pressure (-2.9 +/- 1.7/-1.2 +/- 1.0 mmHg) or average 24 h blood pressure (1.5 +/- 1.3/1.2 +/- 0.7 mmHg). There were no significant differences in the waking and sleeping times between the two seasons., Conclusions: Office, home and daytime ambulatory blood pressure levels were higher in winter than they were in summer in patients with essential hypertension. However, the seasonal variations in average 24 h blood pressure may be small because of the lack of changes in night-time blood pressure.

Objective: To examine the acute effects of alcohol on blood pressure and erythrocyte cation concentrations in patients with essential hypertension., Design: An alcoholic drink or an isocaloric control drink was given during supper in random order on different days, and blood pressure and erythrocyte cation concentrations were measured before and 2 h after the meal., Methods: The subjects were 21 men with essential hypertension who habitually drank alcohol. Blood pressure was measured with a semi-automated sphygmomanometer, and erythrocyte cation concentrations were measured by flame photometry after haemolysis with distilled water., Results: Blood pressure decreased after both drinks, but the decrease was significantly larger after the alcoholic drink than after the control drink. There was a significant difference between the changes in erythrocyte sodium caused by the alcoholic and the control drink. Furthermore, there were significant positive correlations between the fall in blood pressures and the decrease in erythrocyte sodium concentration., Conclusion: The predominant acute effect of alcohol ingestion in patients with hypertension is blood pressure reduction, and it may be associated with a decrease in intracellular sodium.

Aim: To compare the effects of dietary salt on sodium-calcium exchange and the ATP-driven calcium pump in arterial smooth muscle between Dahl salt-sensitive (DS) and salt-resistant (DR) rats., Methods: Aortic rings freshly excised from 16 DS rats and 16 DR rats on a low- (0.3%) or high- (8%) NaCl diet for 4 weeks were superfused with physiological saline and isometric tension was measured. In the presence of 10 mumol/l phentolamine, 10 mumol/l verapamil and 5 mmol/l caffeine, relaxation of a low-Na+ contraction was promoted by external calcium removal., Results: On the high-salt diet, the rate of relaxation at 1.2 mmol/l extracellular sodium (calcium extrusion by calcium ATPase) was significantly lower in aortic rings from DS rats than from DR rats. The increase in the rates of relaxation from 1.2 mmol/l to normal (139.2 mmol/l) extracellular sodium (calcium extrusion by sodium-calcium exchange) was significantly greater with the high-salt diet than with the low-salt diet in rings from DR rats, but it was not different between the high- and low-salt diets in DS rats. The rate of increase in tonic tension by reducing extracellular Na+ from normal to 1.2 mmol/l in the presence of verapamil, caffeine and phentolamine (calcium entry by sodium-calcium exchange) was significantly lower in rings from DS rats than in those from DR rats on the high-salt diet., Conclusions: These observations suggest that the effects of dietary salt on the sodium-calcium exchange system in arterial smooth muscle differ between DS and DR rats and that calcium extrusion by the calcium pump is decreased in DS rats compared with DR rats. The lack of an increase in sodium-calcium exchange in salt-fed DS rats might lead to an elevation in cellular calcium and contribute to the mechanism of hypertension.