Background: Results from previous studies suggested that a blunted response of renal plasma flow (RPF) to angiotensin II infusion during a high-sodium diet (a phenotype associated with nonmodulation) is an intermediate phenotype for essential hypertension.
Objective: To determine whether RPF traits used to investigate nonmodulation have the characteristics of intermediate traits when examined in a population-based sample of adults aged 20-49.9 years.
Design and methods: We examined the frequency distribution of baseline RPF and of its response to All infusion using maximum-likelihood commingling analysis in order to investigate the null hypothesis that the distributions of these traits are unimodal. We also examined the null hypothesis that there is no association between these candidate intermediate traits and the parental history of essential hypertension.
Results: There was some evidence for the commingling of multiple distributions underlying these traits both for women and for men but the commingled distributions overlapped substantially and the inferences about the commingling of distributions were sensitive to the method of RPF measurement, exclusion of outliers, and the method of adjustment for concomitants. There was no statistically significant association between any of the RPF traits and a parental history of essential hypertension.
Conclusions: There is not sufficiently strong evidence to advocate the use of this set of intermediate traits to identify high-risk individuals or to relate genetic variation to the variation in risk of essential hypertension within this age range in the population at large.