Mixture analysis of erythrocyte lithium-sodium countertransport and blood pressure.

Abstract

This study employs multivariate normal mixture analysis, a technique for identifying discrete subgroups within populations, to examine the relation of erythrocyte lithium-sodium (RBC Li + -Na + ) countertransport and blood pressure in a group of 474 healthy adults. Received April 11, 1988; accepted September 23, 1988. recently proposed marker for essential hypertension that has been shown to be associated with high blood pressure in many studies 8 -16 and also to be related to organ-scale abnormalities of potential pathogenetic importance to hypertension. + -Na + countertransport in a normotensive group of blood bank donors could be resolved into two normal subdistributions. It was suggested that individuals in the higher Li + -Na + countertransport subdistribution could be at increased genetic risk for future hypertension, although an association between elevated countertransport and high blood pressure could not be proven because individuals with established hypertension were excluded. We examined the relation of RBC Li + -Na + countertransport and blood pressure in a combined population of normotensive and hypertensive subjects by using a novel bivariate analytic technique to test the hypothesis that high blood pressure cosegregates with elevated RBC Li + -Na + countertransport.

Red blood cell lithium-sodium countertransport in the tecumseh blood pressure study.

“…12 The prevalence of high countertransport is lower (12.9%) in the present population-based sample than in our earlier study (27%), which undoubtedly reflects an overrepresentation of hypertensive subjects in the earlier sample.…”

“…As shown in Figure 1, univariate mixture analysis revealed that the distribution of RBC Li + -Na + countertransport is composed of two groups (p<0.00001 versus one or three groups), which is consistent with our earlier findings. 12 The larger subgroup (n=614, 87.1%) has a mean V^ for Li + -Na + countertransport activity ( Table 28 and is referred to below as the "high countertransport" group. Both groups had a similar proportion of males (57.1% versus 54.6%, high versus normal countertransport, p=0.64 by x 2 ), so that no adjustment for gender differences was necessary in the subgroup comparisons.…”

“…As we have previously described, 12 countertransport values were first adjusted for the effects of gender and for the first-, second-, and third-order power effects of age, weight, and height and for interaction effects of these variables. The resulting adjusted distributions were then examined for the presence of a mixture with simultaneous adjustment for skewness.…”

Erythrocyte Sodium-Lithium Countertransport and Blood Pressure

“…4,35 The findings of increased blood pressure and increased indexes of body weight and fat mass as well as an increased waist/hip ratio in subjects with high SLC, are consistent with earlier reports. 4,35 Linkage analysis was performed with SLC used as a quantitative phenotype. The additive heritabilities of SLC-1 and SLC-2 were 0.42 and 0.49, respectively.…”

“…SLC is continuously distributed with right-skewing in populations, and biometric mixture analysis has suggested that the skewed distribution of SLC is composed of 2 overlapping normally distributed subpopulations. [2][3][4][5] In addition to blood pressure, a number of exogenous factors and traits are associated with variation in SLC activity, including plasma triglyceride 6 and potassium 7 levels, insulin resistance, 8 ethnicity, 9 pregnancy, 10 and nonmodulation of blood pressure in response to changes in dietary sodium. 11 Numerous other potential confounders have been examined, often with inconsistent findings, 12 but it is safe to say that at present, no single trait clearly explains the finding of 2 subpopulations.…”