J R M'Buyamba-Kabangu

Calcium, vitamin D-endocrine system, and parathyroid hormone in black and white males.

SummaryThe serum and urinary calcium, 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), and parathyroid hormone (PTH) were studied in healthy black and white males living in Belgium, and the results were compared to data in blacks of similar age living in Zaïre. Dietary calcium and vitamin D were estimated in a subsample of blacks and whites examined in Belgium. Compared to whites (9.51±0.28 mg%) serum calcium was somewhat lower in blacks (9.26±0.27 mg% in Belgium; 9.19±0.48 mg% in Zaïre). The 24 hour urinary calcium excretion averaged 215.0±16.7 mg% in whites and was higher (P<0.05 or less) than in blacks (115±71 mg% in Belgium; 36±33 mg% in Zaïre). The serum 25OHD levels were similar in whites and blacks evaluated in Zaïre, both being higher (P<0.05 or less) than in blacks living in Belgium. In the latter blacks, an inverse correlation was observed between the 25OHD level and the duration of the stay in a temperate climate. Parathyroid hormone levels were slightly higher in blacks living in Belgium than in the other two groups of subjects. The serum levels of 1,25(OH)2D3 and human vitamin D-binding protein were similar in the three groups of subjects. Dietary calcium averaged 541±152 mg/day in blacks and was significantly (P<0.001) less than in whites (1,203±508 mg/day), whereas no significant difference was observed in dietary vitamin D intake between blacks and whites. It is concluded that calcium intake is low in blacks but stimulation of parathyroid hormone and 1,25(OH)2D3 required to achieve normocalcemia does not occur.

In-Hospital Mortality Among Black Patients Admitted for Hypertension-Related Disorders in Mbuji Mayi, Congo

BACKGROUND As a consequence of hypertension, sub-Saharan Africa faces an epidemic of cardiovascular disease. METHODS We assessed in-hospital mortality among patients admitted for hypertension-related diseases to two city hospitals in Mbuji Mayi, Congo. On admission, we obtained anthropometric measurements, blood pressure, information on cardiovascular risk factors, and on the awareness and treatment of hypertension. We modeled the probability of death, using stepwise logistic regression. RESULTS Of 401 consecutive patients (mean age, 54.3 years; 129 women), 118 (29.4 %) were unaware of their hypertension. Among 283 aware patients (70.6%), 126 (44.5%) were untreated. Systolic/diastolic blood pressure on admission averaged 178/106 mm Hg. In addition to hypertension, 390 patients (97.3%) had other cardiovascular risk factors, including a creatinine clearance below 60 ml/min/1.73 m(2) in 47 subjects (11.7%). Over 15 days (median) of hospitalization, 89 deaths (22.2%) occurred. The multivariable-adjusted probability of death increased with systolic blood pressure (odds ratio (95% confidence interval) for +10 mm Hg, 1.43 (1.15-1.77); P < 0.01), body mass index (+5 kg/m(2), 2.40 (1.39-4.17); P < 0.01), being aware vs. unaware of hypertension (3.17 (1.52-6.61); P < 0.01), and being untreated (2.33 (1.12-4.76); P < 0.05), but it decreased with age (+10 years, 0.65 (0.46-0.92); P < 0.05) and higher creatinine clearance (+10 ml/min/1.73 m(2), 0.71 (0.61-0.82); P < 0.001). CONCLUSIONS The in-hospital mortality among African patients hospitalized for hypertension-related disorders in a Congolese provincial capital city is over 20%. These findings underscore that screening and treatment for hypertension and the prevention of cardiovascular disease should be placed much higher on the political agenda in sub-Saharan Africa.

Intracellular sodium and the response to nitrendipine or atenolol in African blacks.

The relationship between the hypotensive effect of nitrendipine (N), 20 mg/day (n = 17), or atenolol (A), 100 mg/day (n = 17), and the erythrocyte sodium [( Na]i) and potassium [( K]i) concentrations was investigated in hypertensive African blacks during a randomized double-blind study. After 6 weeks, both treatments significantly reduced supine and standing blood pressures; however, the magnitude of the decrease in supine systolic (-22.0 +/- 2.0 vs -12.1 +/- 3.4 mm Hg) and diastolic (-14.1 +/- 1.3 vs -7.6 +/- 2.1 mm Hg) pressures and in standing diastolic pressure (-16.0 +/- 1.7 vs -9.2 +/- 2.0 mm Hg) was more pronounced (p less than 0.05) in the N-treated than in the A-treated group. Pulse rate, plasma aldosterone, and plasma renin activity were lower (p less than 0.05) in the A-treated patients. Neither treatment had significant influence on [Na]i, [K]i, or ouabain-sensitive sodium efflux. The N-induced changes in supine systolic and diastolic pressure correlated (p less than 0.05) with age (r = -0.65 and r = -0.58, respectively) and pretreatment plasma renin activity (r = 0.71). Multiple regression analysis demonstrated a negative association between pretrial [Na]i and the change in systolic pressure during N treatment that was independent of age, pretreatment blood pressure, and change in pulse rate. Age and the change in supine pulse rate were also independently correlated with the change in diastolic pressure during N treatment. The results show a greater antihypertensive efficacy of N than A in the patients entered in this study and suggest that a higher intracellular sodium concentration could predict a better hypotensive response to N.

Calcium entry blockade or beta‐blockade in long‐term management of hypertension in blacks

The long‐term efficacy of nitrendipine and acebutolol was assessed during a 40‐week double‐blind randomized trial in 60 hypertensive blacks. Nitrendipine (mean dose 32 mg/day) and acebutolol (414 mg/day) were administered in monotherapy in increasing dosage and mefruside was added in patients not controlled by monotherapy. The recumbent and standing blood pressures were reduced (P < 0.01 or less) during monotherapy with nitrendipine and acebutolol, but the magnitude of blood pressure reduction was greater (P < 0.05 or less) during nitrendipine dosing. Pulse rate decreased (P < 0.01) during acebutolol whereas nitrendipine induced a nonsignificant increase. Both treatments induced no changes in serum electrolytes, creatinine, urea, uric acid, lipids, plasma renin activity, and plasma and urinary aldosterone. The overall incidence of side effects was similar with both treatments but four patients discontinued nitrendipine because of headache. The addition of mefruside to nitrendipine or acebutolol produced a further fall of blood pressure in patients not controlled with monotherapy. Monotherapy with nitrendipine or acebutolol offers an effective, safe first‐line antihypertensive treatment in blacks entered in this study; with the described dosages and therapeutic schedule, nitrendipine was somewhat more effective than acebutolol.

Changes in erythrocyte sodium and plasma lipids associated with physical training

The intracellular concentrations and transmembrane fluxes of Na+ and K+ in erythrocytes, and plasma lipids were investigated in 30 middle-aged volunteers, before and after physical training. During the first 4 months of the study, half of the subjects (group A) were subjected to a training programme (3 h/week), while the others (group B) served as controls. At the end of the control period the group B subjects also underwent a period of training. At the end of the training, in both experimental groups, the intra-erythrocyte Na+ concentration was decreased (P less than 0.001); the magnitude of this decrease was related to the increase achieved in physical working capacity (r = -0.44; P less than 0.05). After training the activity of the erythrocyte Na+-Li+ counter-transport system was decreased (P less than 0.001) in both groups, whereas Na+,K+ cotransport activity was increased (P less than 0.001). The training intervention did not affect erythrocyte ouabain-sensitive 86Rb uptake, or the calculated rate constant for ouabain-sensitive Na+ efflux. Furthermore, the plasma concentrations of high density lipoproteins (HDL)2- and HDL3-cholesterol (P less than 0.001) markedly increased in both groups during the training period. However, these changes were not significantly correlated with the observed training-induced changes in erythrocyte transmembrane cationic fluxes. It is concluded that physical training decreases intra-erythrocyte Na+ concentration. No significant associations between training-induced changes in plasma lipids and erythrocyte sodium balance could be demonstrated.

Relative potency of a beta-blocking and a calcium entry blocking agent as antihypertensive drugs in black patients

SummaryThe short-term efficacy of nitrendipine (N) as a first stage antihypertensive drug in black patients has been assessed and compared with acebutolol (A) in a double-blind study. Forty patients were randomized and after a 4 week run-in period on placebo, the active treatment was administered for 6 weeks starting with 20 mg N or 200 mg A once daily. The dose was increased up to 60 mg N or 600 mg A as needed. Nitrendipine appeared to be more efficient than acebutolol in reducing blood pressure and the N-induced fall in blood pressure was achieved after 2 weeks. After 2 and 6 weeks on N, the recumbent blood pressure was decreased by 13% and 12% for the systolic and by 14% and 11% for the diastolic pressure. The concurrent decreases in the A group averaged 4% and 5% for the systolic and 5% and 10% for the diastolic pressure after 2 and 6 weeks. Pulse rate and plasma renin activity in the N group were slightly increased and body weight was decreased at the end of the active treatment period.

Erythrocyte concentrations and transmembrane fluxes of sodium and potassium and biochemical measurements during the menstrual cycle in normal women.

The erythrocyte concentrations and the transmembrane fluxes of sodium and potassium were investigated in 20 normal women during the two stages of the menstrual cycle. Half of the women were using oral contraceptives and the other half were not. In women with a normal menstrual cycle the erythrocyte sodium concentration and the ouabain-insensitive total potassium efflux were lower in the luteal than in the follicular phase. Intracellular potassium concentration, ouabain-sensitive rubidium 86 uptake and the furosemide-sensitive sodium and potassium efflux did not differ significantly between the two periods of the cycle. No cycle-related variation in sodium or potassium intracellular concentration was observed in women using oral contraceptives. In these women, however, the ouabain-sensitive 86Rb uptake was increased in the second part of the menstrual cycle. In each woman with a normal menstrual cycle the plasma progesterone, renin activity, angiotensin II, plasma aldosterone concentration, and urinary aldosterone excretion increased during the luteal phase. The increment in the plasma renin activity, plasma angiotensin II, and plasma and urinary aldosterone indicate a stimulation of the renin-aldosterone axis in this menstrual period. During the same phase, serum cholesterol was decreased significantly. When the women using oral contraceptives were compared to those not using them, the renin-aldosterone axis was already stimulated during the first part of the cycle; no further stimulation occurred during the second part.

Erythrocyte concentrations and transmembrane fluxes of sodium and potassium in essential hypertension: Role of intrinsic and environmental factors

SummaryThe intraerythrocyte sodium concentration is increased in the erythrocytes of Zaïrean Bantu with untreated hypertension, while the red blood cell potassium is not differenent from that of normotensive subjects. Compared with whites, normotensive healthy blacks have a higher intracellular concentration of sodium due to a depressed activity of the sodium-potassium pump. Normotensive healthy males with a positive familial background of hypertension display higher erythrocyte sodium and lower cotransport activity. None of the two measurements offer a clear-cut genetic marker of essential hypertension. In healthy women, the erythrocyte sodium concentration is lowered during the luteal as compared with the follicular phase of the menstrual cycle. This variability explains the difference observed between men and women. A low-sodium diet stimulates the activity of the sodium-potassium ATPase pump, which leads to a decrease in the erythrocyte sodium concentration. Both alterations reverse only slowly during sodium repletion. It is therefore suggested that an adequate matching for race, sex, stage of the menstrual cycle (in women), family history of hypertension, and the amount of sodium in the diet should be a prerequisite for valid conclusions when interpreting the erythrocyte concentration and fluxes of sodium.

Efficacy of newer versus older antihypertensive drugs in black patients living in sub-Saharan Africa

To address the epidemic of hypertension in blacks born and living in sub-Saharan Africa, we compared in a randomised clinical trial (NCT01030458) single-pill combinations of old and new antihypertensive drugs in patients (30–69 years) with uncomplicated hypertension (140–179/90–109 mm Hg). After ⩾4 weeks off treatment, 183 of 294 screened patients were assigned to once daily bisoprolol/hydrochlorothiazide 5/6.25 mg (n=89; R) or amlodipine/valsartan 5/160 mg (n=94; E) and followed up for 6 months. To control blood pressure (<140/<90 mm Hg), bisoprolol and amlodipine could be doubled (10 mg per day) and α-methyldopa (0.5–2 g per day) added. Sitting blood pressure fell by 19.5/12.0 mm Hg in R patients and by 24.8/13.2 mm Hg in E patients and heart rate decreased by 9.7 beats per minute in R patients with no change in E patients (–0.2 beats per minute). The between-group differences (R minus E) were 5.2 mm Hg (P<0.0001) systolic, 1.3 mm Hg (P=0.12) diastolic, and 9.6 beats per minute (P<0.0001). In 57 R and 67 E patients with data available at all visits, these estimates were 5.5 mm Hg (P<0.0001) systolic, 1.8 mm Hg (P=0.07) diastolic and 9.8 beats per minute (P<0.0001). In R compared with E patients, 45 vs 37% (P=0.13) proceeded to the higher dose of randomised treatment and 33 vs 9% (P<0.0001) had α-methyldopa added. There were no between-group differences in symptoms except for ankle oedema in E patients (P=0.012). In conclusion, new compared with old drugs lowered systolic blood pressure more and therefore controlled hypertension better in native African black patients.

Intracellular concentration and transmembrane fluxes of sodium and potassium in erythrocytes of normal men and women

SummaryThe intracellular concentration and transmembrane fluxes of sodium and potassium were studied in the red blood cells of normal men and women in the two halves of their menstrual cycle.Compared to men, the intra-erythrocyte sodium concentration was lower in women during the second half of the menstrual cycle. These two groups were similar for Na+, K+-ATPase pump activity estimated from the ouabain-sensitive86rubidium-uptake and for the furosemide-sensitive sodium and potassium efflux.Women in the first half of the menstrual cycle, had intra-erythrocyte sodium concentration similar to men, but their furosemide-sensitive sodium efflux was lower.A lower intra-erythrocyte sodium concentration was observed in the second half as compared to the first half of the menstrual cycle in women.No significant difference was observed in the intra-erythrocyte potassium concentration and transmembrane fluxes of potassium in men and women in either half of the menstrual cycle.Therefore one should take into account sex-related variability when studying cationic fluxes and concentrations in red blood cells of men and women.