Epidemiology of Blood Pressure, Insulin, Salt Transport

BACKGROUND:

Insulin levels are consistently related to blood pressure, obesity, and blood lipids. Insulin level correlation with sodium-lithium countertransport is limited to only one available study done in white, normotensive, predominantly normal weight women aged 45-52. The relationship between cellular sodium-hydrogen exchange activity and hypertension has been studied in rats and in a small study in humans. Correlation of this transport with weight, fasting insulin and lipid levels, and sodium-lithium countertransport was not available in 1989.

DESIGN NARRATIVE:

The study was cross-sectional. Subjects were stratified by weight: plus or minus 10 percent of desirable weight; 11 to 30 percent over desirable weight; and 30 percent over desirable weight; and by diastolic blood pressure: 80; 80-89; 90-99 mmHg. Blood pressure, height, weight, waist and hip girth, skinfold, fasting and post-glucose load insulin, glucose, lipids, creatinine, maximal rates of red blood cell sodium-lithium countertransport and platelet sodium-hydrogen exchange, pH, and calcium concentrations were measured. The strength and independence among these continuous variables were measured by Pearson correlations, partial correlations, and multiple regressions within each stratum, and if appropriate, over all strata. The study examined the hypotheses that: part of the relationship between obesity and blood pressure was due to insulin effects and/or lipid effects on ion transport; the relationship between ion transport and blood pressure was related to an abnormality of sodium-hydrogen exchange, for which the observed increase in sodium-lithium countertransport was a marker; increased blood pressure was related to the alteration of intracellular pH and/or calcium concentration.