A comparison of nephron number, glomerular volume and kidney weight in Senegalese Africans and African Americans

Abstract

Background. Low nephron number is determined in utero and is a proposed risk for essential hypertension. Glomerular volume is inversely correlated with nephron number, and genetic and environmental factors that determine nephron number are thought to determine glomerular volume. This study compared total glomerular (nephron) number (Nglom), mean glomerular volume (V glom) and kidney weight in two geographically separated black populations with significant common genetic ancestry.Methods. Unbiased stereology was used to determine Nglom and Vglom in kidneys collected at coronial autopsy in an age-and sex-matched sample of 39 adult Africans from Dakar in Senegal, West Africa and 39 African Americans from Mississippi in the USA.Results. African Americans were taller and heavier than their Senegalese counterparts. Nglom was remarkably similar-with a geometric mean of 937 967 in Senegalese and 904 412 in African Americans (P = 0.62). V glom was correlated inversely with Nglom and directly with body surface area in both groups, but Vglom was 54% greater in African Americans than in Senegalese Africans [8.30 ± 2.92 (SD) and 5.38 ± 1.25 μm3 × 106, respectively] and remained significantly larger (38%) after adjustment for body size. Vglom increased with age in African Americans, but not in the Senegalese. Kidney weight was larger in African Americans (P < 0.0001), but kidney-to-body weight ratio was not different between groups.Conclusions. Despite similar nephron numbers, a common genetic constitution, and even in relation to current body size, African Americans have larger Vglom than Senegalese subjects. This may mark exposure to environmental stressors or hereditary traits concentrated in the population's relocation to North America. © The Author 2009. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved.