Charge movements during the Na+-Ca2+ exchange in heart sarcolemmal vesicles.

AUTOR(ES)

Caroni, P

RESUMO

The Na+-Ca2+ exchange was studied in a highly purified vesicular preparation derived from heart sarcolemma. The initial velocity of the Na+-driven Ca2+ influx, which was monitored continuously with a specific electrode, was 15 nmol/mg of protein per sec; the total Ca2+-accumulation capacity was 80 nmol/mg of protein. The Na+-Ca2+ exchange generated a current that was compensated for by the uptake of tetraphenylphosphonium in (Ph4P+) (when the latter was present in the medium), the influx of K+, and the efflux of Cl-. The movements of Ph4P were followed with a specific electrode. Ca2+ in the concentration range 3-50 microM induced an increase in the permeability of the sarcolemmal membrane to K+. Under conditions of optimal charge neutralization by K+ (i.e., in the presence of valinomycin), the Km (Ca2+) of the exchanger was 1.5 microM. The Na+-Ca2+ exchange was inhibited by chlorpromazine and was not inhibited by vanadate.

Documentos Relacionados

• Inner sarcolemmal leaflet Ca(2+) binding: its role in cardiac Na/Ca exchange.
• Measurement of reversal potential of Na+-Ca2+ exchange current in single guinea-pig ventricular cells.
• Roles of Two Ca2+-binding Domains in Regulation of the Cardiac Na+-Ca2+ Exchanger*
• Inhibition of the sarcoplasmic reticulum Ca2+ pump with thapsigargin to estimate the contribution of Na+-Ca2+ exchange to ventricular myocyte relaxation
• Current-voltage relations and steady-state characteristics of Na+-Ca2+ exchange: characterization of the eight-state consecutive transport model.