Kinetic characteristics of the erythrocyte sodium-lithium countertransporter in subjects with coronary artery disease

Sodium-lithium countertransport activity, external affinity for sodium (kNa) and maximal rate of turnover (Vmax), were characterized in 21 male subjects (aged 45 to 65 years) with angiographically proven coronary artery disease; these were compared with a matched group of healthy controls. No significant differences in countertransport activity were noted between the coronary artery disease patients and the healthy controls. By contrast, the median [range] kNa in the coronary artery 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 Vmax (controls 0.403 ± 0.187 ν coronary artery disease group 0.248 ± 0.121 mmol Li/L RBC/h; P< .01). The findings suggest that disturbed behavior of the sodium-lithium countertransporter is not confined to hypertension but may represent a broader-based membrane dysfunction associated with vascular disease.