Vascular Reactivity and Salt Sensitivity in Normotensive and Hypertensive Adult Nigerians

There are not many studies designed to study the relationship between vascular reactivity and salt sensitivity in a black population. Fifty-two hypertensive (HT) and forty-seven age-matched normotensive (NT) Nigerian subjects took part in the study after informed consent was obtained from them. Ethical clearance was obtained from the College of Medicine of the University of Lagos. Vascular hyperreactivity in response to the Cold Pressor Test (CPT) was determined as a change in systolic blood pressure (ΔSBP) or diastolic blood pressure (ΔDBP) ≥ +15mmHg. This was determined before and after salt-loading with 200mmol Na+/day for 5 days. Salt sensitivty was determined as a change in mean arterial blood pressure (ΔMABP) ≥+5mmHg. Salt-loading led to significant increases in SBP among NT (p = 0.03) and among HT (p = 0.0001) subjects; DBP increased significantly only among HT subjects (p = 0.0003). Systolic and diastolic hyperreactivity were higher among HT (49% and 39% respectively) compared to NT (44% and 39% respectively) at baseline. However systolic hyperreactivity (SHP) increased from 44% to 64% after salt-loading among the NT while diastolic hyperreactivity (DHP) reduced from 39% to 36%. Among the HT, both SHP and DHP reduced from 49% to 33% and from 41% to 31% respectively following salt-loading. Salt sensitivity was higher among HT (56%) compared to NT 34%. Salt sensitivity was positively correlated with systolic reactivity before salt (r = 0.33; p < 0.05) and after salt (r = 0.25; p > 0.05) but negatively correlated with diastolic reactivity before salt (r = -0.38; p < 0.05) and after salt (r = -0.40; p < 0.05) among NT. These results suggest that systolic hyperreactivity may be a significant determinant in the development of salt sensitive hypertension among this population.Keywords: Vascular reactivity, Salt sensitivity hypertension, Blood pressur

Vascular reactivity and salt sensitivity in normotensive and hypertensive adult Nigerians

There are not many studies designed to study the relationship between vascular reactivity and salt sensitivity in a black population. Fifty-two hypertensive (HT) and forty-seven age-matched normotensive (NT) Nigerian subjects took part in the study after informed consent was obtained from them. Ethical clearance was obtained from the College of Medicine of the University of Lagos. Vascular hyperreactivity in response to the Cold Pressor Test (CPT) was determined as a change in systolic blood pressure (ΔSBP) or diastolic blood pressure (ΔDBP) ≥ +15mmHg. This was determined before and after salt-loading with 200mmol Na+/day for 5 days. Salt sensitivty was determined as a change in mean arterial blood pressure (ΔMABP) ≥+5mmHg. Salt-loading led to significant increases in SBP among NT (p = 0.03) and among HT (p = 0.0001) subjects; DBP increased significantly only among HT subjects (p = 0.0003). Systolic and diastolic hyperreactivity were higher among HT (49% and 39% respectively) compared to NT (44% and 39% respectively) at baseline. However systolic hyperreactivity (SHP) increased from 44% to 64% after salt-loading among the NT while diastolic hyperreactivity (DHP) reduced from 39% to 36%. Among the HT, both SHP and DHP reduced from 49% to 33% and from 41% to 31% respectively following salt-loading. Salt sensitivity was higher among HT (56%) compared to NT 34%. Salt sensitivity was positively correlated with systolic reactivity before salt (r = 0.33; p \u3c 0.05) and after salt (r = 0.25; p \u3e 0.05) but negatively correlated with diastolic reactivity before salt (r = -0.38; p \u3c 0.05) and after salt (r = -0.40; p \u3c 0.05) among NT. These results suggest that systolic hyperreactivity may be a significant determinant in the development of salt sensitive hypertension among this population

Epithelial sodium channel blockade and new β-ENaC polymorphisms among normotensive and hypertensive adult Nigerians

We sought to determine the effect of amiloride on blood pressure (BP) and the presence of polymorphisms of the β-subunit of the epithelial sodium channel (ENaC) among normotensive (NT) and hypertensive (HT) Nigerians. Healthy volunteers—47 NT and 53 age-matched HT were recruited after giving informed consent. Subjects were salt-loaded with 200 mmol of NaCl daily for 5 days. Following a week washout period, salt-loading was repeated in addition to the administration of 5 mg amiloride daily for five days. Blood pressure, plasma and urine electrolytes were measured at baseline, after salt-loading and after salt-loading plus amiloride. PCR amplicons were sequenced for β-ENaC polymorphisms. Salt-loading led to a significant increase (p < 0.05) in SBP among NT and HT and in DBP (p < 0.001) only among HT. Amiloride reduced SBP and DBP to below baseline levels in NT (p < 0.05) and HT (p < 0.001) subjects. Five of the subjects had the β-T594M polymorphism, HT 3/53; NT 2/47 (p = 0.75). Four previously unreported β-ENaC mutations were recorded: E632V and E636V, respectively, among two HT subjects, D638Y in another HT and L628Q in one NT subject. We showed the presence of β-ENaC polymorphisms among our populace and the possible usefulness of amiloride as a single antihypertensive among Nigerians

Volume regulatory hormones and plasma volume in pregnant women with sickle cell disorder

Background: Sickle cell disease (haemoglobin SS (HbSS)) mainly affects those of West African origin and is associated with hypervolaemia. Plasma volume rises by up to 50% in normal pregnancy but was previously found to be paradoxically contracted in late sickle cell pregnancy. The renin–angiotensin–aldosterone system is activated very early in human pregnancy to support the plasma volume expansion. We hypothesised that activation of the renin–angiotensin–aldosterone system would be blunted in pregnant women with sickle cell disease. Materials and methods: We measured plasma volume and concentrations of plasma renin, angiotensinogen, aldosterone and other volume-related hormones in a cross-sectional study of pregnant and non-pregnant Nigerian women with HbSS or HbAA. Results: Plasma volume was higher in non-pregnant HbSS than HbAA women, but had not risen by 16 weeks, unlike plasma volume in HbAA women. The concentration of plasma renin also rose significantly less by 16 weeks in HbSS; angiotensinogen and aldosterone concentrations increased. Conclusions: The lower plasma renin concentration at 16 weeks with HbSS could be either primary or secondary to vasoconstriction related to inadequate vasodilator activity. The contracted plasma volume might then stimulate aldosterone synthesis by non-angiotensin II dependent stimulation. Studies of vasodilators such as nitric oxide, vasodilator eicosanoids or the PlGF/VEGF/sFlT-1 axis in pregnant HbSS and HbAA women will test this hypothesis