[The effect of OCl- and Ag+ on active and passive calcium transport in the sarcoplasmic reticulum]

After hypochlorite (OCl-) treatment of the aortic smooth muscle sarcoplasmic reticulum (SR), the membrane microviscosity increases considerably in "bound" lipid regions in comparison with protein-free regions. OCl- induces the inhibition of active and the enhancement of passive calcium transport in SR. Treatment of SR vesicles with Ag+ and then with OCl- (but not in the reverse order) leads to the enhancement of the activating effect of OCl- on passive calcium release from the vesicles. It is concluded that the enhancement effect is due to the OCl(-)-induced increase in the passive permeability of the SR membrane for Ca2+ as a result of pore formation in the lipid bilayer.