Effect of salt loading and gender influences on plasma atrial natriuretic peptide levels and cardiovascular parameters in normotensive and hypertensive Nigerians

Abstract

Background: Prevalence of hypertension is higher among Sub-Saharan Africans than whites and there is a sex difference in the prevalence. Though, salt retention has been implicated in pathogenesis of hypertension, the basis is not completely known. Atrial natriuretic peptide (ANP) might play a role.

Method: 43 apparently healthy normotensive male and female Nigerians and 37 aged-matched hypertensive counterparts were orally administered 11.6g of dietary salt each per day for 5 days. Their plasma ANP levels, heart rate (HR), systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MABP) were determined before and after salt loading.

Results: Normotensive and hypertensive male and female subjects had similar basal ANP levels. However, salt loading significantly raised the ANP concentrations (p = 0.0001) in normotensive subjects but not significantly in hypertensive counterparts. ANP levels rose significantly in the normotensive males (p = 0.0024) and females (p = 0.0002) but not significantly in the hypertensive counterparts. Besides, salt significantly decreased HR in normotensive (p = 0.0095) and hypertensive (p = 0.0397) subjects but increased SBP (p < 0.01) and MABP (p< 0.01) in both study groups and DBP (p = 0.0014) in hypertensive group only. SBP, DBP and MABP were all significantly elevated (p < 0.05) in hypertensive males and females but not significantly in normotensive females.

Conclusion: Although, basal ANP levels were similar in the study normotensive and hypertensive subjects, other findings in this study suggest that ANP as well as female gender could ameliorate increased blood pressure response to salt loading especially in a normotensive state.

Keywords: Atrial natriuretic peptide, blood pressure, salt loading, gender, hypertension