Solubilization and reconstitution of the sarcolemmal Na+-Ca2+ exchange system of vascular smooth muscle.

The Na+-Ca2+ exchange system of the sarcolemma of rat mesenteric artery was solubilized and reconstituted in soybean phospholipid vesicles. In the reconstituted system, the exchange process showed about 4-fold higher specific activity compared to that of native vesicles. The inhibitory effect of monensin and the stimulatory effect of valinomycin in the presence of K+ on Na+ gradient-dependent Ca2+ uptake were preserved and were pronounced in the reconstituted system. The stimulation by valinomycin indicates that the exchange process is electrogenic. Thus, the stoichiometry, the characteristics and the mechanism of action which were difficult to study in the native vesicles can now be determined conveniently using the reconstituted system. Also, solubilization and reconstitution of the exchange system confirms its existence in vascular smooth muscle.