Erythrocyte sodium-lithium countertransport: relationship with plasma renin activity, aldosterone and atrial natriuretic peptide in a population study.

The objective of this study was to investigate the relationships between erythrocyte Na-Li countertransport, plasma renin activity (PRA), plasma aldosterone and plasma atrial natriuretic peptide (ANP) in a population-based study, in a cross-sectional observation of a randomly selected sample of a male working population, conducted at the Medical Care Center at the Olivetti Factory in Pozzuoli (Naples). One hundred and seventy-nine male employees aged 45.3 +/- 6.8 years (mean +/- SD), all on unrestricted diet and on no pharmacological treatment were studied. Statistical associations between Na-Li countertransport activity and the hormonal factors being studied were investigated, with control for the possible confounding effects of age, BP and sodium intake. Na-Li countertransport was significantly and positively associated with plasma aldosterone concentration (r = 0.228, P < 0.01) but not with PRA or plasma ANP. Men in the highest quartile of the Na-Li countertransport distribution had significantly higher plasma aldosterone levels than men in the other quartiles (P < 0.01) and this difference was independent of age, body mass, PRA, urinary sodium excretion and blood pressure. It is concluded that plasma aldosterone levels are enhanced and disproportionately high relative to plasma renin activity in individuals with high Na-Li countertransport, independently of known potential confounders.