Erythrocyte cation cotransport and countertransport in essential hypertension.

The relation of red blood cell sodium-stimulated lithium countertransport to blood pressure (BP) and prevalence of hypertension was assessed in univariate and multivariate analyses for 2,748 men and women aged 25-74 years who participated in the baseline examination of the Gubbio Population Study in north central Italy. Since age-specific countertransport values were consistently higher for men than women, all analyses were done for men and women separately. In simple correlation analyses, countertransport was significantly related to systolic and diastolk BP in both sexes (r values 0.107-0.163). In age-adjusted analyses, countertransport was significantly related to BP level of both men and women not receiving antihypertensive treatment; mean levels were high for hypertensive persons receiving antihypertensive therapy compared with normotensive persons. Age-adjusted prevalence rates of hypertension were progressively higher for both sexes in successively higher quintiles of countertransport, almost twice as high for those in the highest quintile compared with those in the lowest quintile. Correspondingly, age-adjusted logistic regression analyses showed countertransport to be related significantly to prevalence of hypertension for both men and women (p<0.001). Since age, body mass index, plasma total cholesterol, uric acid, glucose, urinary sodium/potassium excretion, pulse, and (for men) daily alcohol intake also were significantly correlated with BP, and in some instances with countertransport, relation of countertransport to BP was also assessed in multivariate analyses with control for these variables. For men and women, multiple logistic coefficients for the relation of countertransport to prevalence of hypertension were significant (p<0.05) or borderline significant ( 0 . 0 5 < / J < 0 . 1 0 ) ; a person with a high countertransport value was 1.3-1.9 times more likely to be hypertensive than a person with a low value. These findings indicate that the cross-sectional relation between countertransport and hypertension generally remains significant with control for other traits known to be related to hypertension. However, prospective data are lacking as to whether countertransport is an independent risk factor for incidence of hypertension. Such data are needed for further clarification of the relation of high countertransport to the etiology of hypertension. {Hypertension 1989;13:408-415) S everal studies have reported statistically significant relations between red blood cell (RBC) sodium-stimulated lithium (Na-Li) countertransport and blood pressure (BP). Most of these have been clinic-based case-control investigations contrasting mean Na-Li countertransport in people with normal and high blood pressure. '-10 Only a few have been population-based, involving limited samples narrow in age range or otherwise selected."-18 All to date have been cross-sectional. A key question is the meaning of the positive findings of these studies, in terms of still unresolved issues of the role of electrolyte metabolism...

Section: Discussionsupporting

confidence: 88%

Sodium-lithium countertransport and blood pressure: the Gubbio Population Study.

Laurenzi

Trevisan

1989

“…416 ' 48 Chronic hypokalemia has been reported to increase countertransport activity. 49 None of our subjects was hypokalemic (mean, 4.4 ± 0.4 mEq/L; range, 3.7-5.5 rnEq/L), and serum K + within the normal range did not correlate with countertransport activity, in agreement with one earlier report 21 but not with that of Behr et al, 17 who noted an inverse correlation of serum K + and countertransport. Finally, the observation of Brugnara et al 45 relating levels of stimulated plasma renin activity (1 hour after i.v.…”

Section: * 6061supporting

confidence: 91%

Red blood cell Li+-Na+ countertransport, Na+-K+ cotransport, and the hemodynamics of hypertension.

Weder¹,

Fitzpatrick

Torretti

et al. 1987

SUMMARY Red blood cell Li+ -Na + countertransport and Na + -K + cotransport activities, home blood pressure, invasive systemic hemodynamics, and limb venous compliance were measured in 65 white men (23 normotensive, 22 borderline hypertensive, and 20 mild essential hypertensive subjects). Li + -Na + countertransport activity was positively and significantly correlated with subject-determined home systolic blood pressure (r = 0.31, p < 0.02) and with directly measured systolic (r = 0.29, p<0.02) and diastolic (r=0.27, p<0.03) blood pressures in the hemodynamic laboratory, independent of potential confounding variables. Analysis of the hemodynamic determinants of blood pressure revealed a significant positive correlation of countertransport with vascular resistance (r=0.30, p<0.02) but not with cardiac output or cardiac index. High red blood cell Na + -K + cotransport activity was not independently associated with hypertension or with a characteristic hemodynamic pattern but was related to decreased venous compliance. Red blood cell Li + -Na + countertransport deserves further study as a marker for the genetic substrate of human essential hypertension. Red cell Na + -K + cotransport may be altered secondarily by factors related to high blood pressure and seems to be a valid marker for abnormalities of the venous system in hypertension. (Hypertension 9: 459-466, 1987) KEY WORDS • lithium-sodium countertransport • sodium-potassium cotransport bumetanide • vascular resistance • venous compliance I NCREASED systemic vascular resistance is the hemodynamic hallmark of established human essential hypertension. Borderline hypertension results from elevated cardiac output in about a third of patients, but even in such "hyperkinetic" hypertensive patients, vascular resistance is considered to be inappropriately elevated for the prevailing cardiac output.' Although structural changes may reinforce and amplify the development of elevated vascular resistance, 2 the events initiating hypertension can more plausibly

“…26 The consequent overestimation of Li + -Na + countertransport, which is calculated as the difference in Li + efflux in Na + and countertransport, however, the relation is inverse and is actually improved by adjustment. We can offer no explanation for the cause of this correlation, as the mechanisms relating high RBC Li + -Na + countertransport and hypertension are still uncertain, but the finding of a significant inverse relation in the subgroup with higher MAP provides further support for the contention that Li + -Na + countertransport or an analog system is intimately linked to the pathophysiological basis of hypertension in some individuals.…”

Section: Resultsmentioning

confidence: 99%

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

Weder

Schork

1989

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.