Impairment of renal sodium excretion in tropical residents – phenomenological analysis |
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Authors: | S K Arthur P A Aryee J Amuasi I F A Hesse R K Affram |
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Institution: | (1) Department of Physiology, University of Ghana Medical School, P.O.Box 4236 Accra, Ghana, GH;(2) Department of Medicine and Therapeutics, University of Ghana Medical School, P. O. Box 4263, Accra, Ghana, GH;(3) Department of Medicine and Therapeutics, nuclear medicine unit; University of Ghana Medical School, P.O. Box 4263, Accra, Ghana, GH |
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Abstract: | There is evidence of impaired renal sodium excretion in salt-sensitive African Blacks. A decreased rate of renal sodium chloride
(NaCl) excretion, low plasma renin activity and a tendency to elevated blood pressure are the hallmarks of salt sensitivity.
Recent evidence indicates that increased proximal and distal tubular fluid reabsorption in some tropical residents may explain
the impaired sodium excretion in these people. In this study of a cohort population, we speculated that subjects selected
from that population might be salt-sensitive. We therefore measured the sodium balance in 10 normotensive male subjects over
10 consecutive days, after they had ingested a normal or a high amount of sodium, as NaCl (salt) in their diet. We quantified
their renal sodium excretion rate by phenomenological analysis of their sodium balance data. We also measured plasma renin
activity for 7 consecutive days in a separate group of 6 male and 4 female subjects in order to assess the state of their
renin/angiotensin system. We selected all our subjects from a cohort population of 269 subjects randomly selected from a community
known to have a high prevalence of primary hypertension. Our data on two separate groups of subjects from the same cohort
population revealed delayed renal sodium excretion with t
1/2 of about 5 days, compared to published data for normal individuals with t
1/2 of less than 24 h. Also, plasma renin activity levels were low. Hence, our subjects are salt-sensitive. Quantification of
their renal impairment is important for various reasons: it heightens one’s appreciation of the problem of salt retention
in African Blacks who are salt-sensitive and it also underlines the importance of the need for further research into the benefits
of dietary salt restriction for reducing cardiovascular mortality in African populations, as has been done in some Western
countries.
Received: 4 March 1999 / Accepted: 12 May 1999 |
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Keywords: | Tropical environment Sodium homeostasis Water balance Primary hypertension Salt-sensitivity |
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