KINETIC CHARACTERISTICS OF THE ERYTHROCYTE SODIUM-LITHIUM COUNTERTRANSPORTER IN SUBJECTS WITH CORONARY-ARTERY DISEASE

Sodium-lithium countertransport activity, external affinity for sodium (k(Na)) and maximal rate of turnover (V-max), were characterized in 2 1 male subjects (aged 45 to 65 years) with angiographically proven cor onary artery disease; these were compared with a matched group of heal thy controls. No significant differences in countertransport activity were noted between the coronary artery disease patients and the health y controls. By contrast, the median [range] k(Na) in the coronary arte ry disease group (8.5 [2.6 to 30.5] mmol/L Na) was significantly lower than that in the controls (59.9 [5.9 to 240.5] mmol/L Na; P <.0001). This reduction was accompanied by a significantly lower mean V-max (co ntrols 0.403 +/- 0.187 v coronary artery disease group 0.248 +/- 0.121 mmol Li/L RBC/h; P <.01). The findings suggest that disturbed behavio r of the sodium-lithium countertransporter is not confined to hyperten sion but may represent a broader-based membrane dysfunction associated with vascular disease.