NADH-LINKED ELECTRON-TRANSFER INDUCES CD2-MEMBRANE VESICLES( MOVEMENTIN CORN ROOT PLASMA)

The rate of electron transfer from NADH to ferricyanide associated wit h corn root plasma membrane vesicles was not significantly affected by the presence of Ca2+, Cd2+, Zn2+, or Co2+, However, unlike Ca2+, othe r tested divalent cations induced an electron transfer-dependent incre ase in light scattering by the vesicles, The efficacy in inducing the light scattering increase followed the order of Cd2+>Zn2+>Co2+. The ex tent of the light scattering change increased as the concentration of added Cd2+ increased, Using phase contrast microscopy, the increase in light scattering was related to an expansion of the vesicles. Accompa nying the volume increase, a decrease of Cd2+ concentration in the ext ernal space was observed by the use of Arsenazo III, a metallochromoph ore specific for divalent cations, Under a specified electron transfer condition, a similar percentage of decrease over a wide range of init ial Cd2+ concentration was detected. The presence of A23187 decreased the rate and extent of light scattering increase and its associated Cd 2+ concentration change, However, A23187 had no effect on scattering c hanges already established by the electron transfer and Cd2+. These re sults suggest that the NADH linked electron transfer reaction may indu ce a Cd2+ uptake by the vesicles of corn root plasma membrane with ins ide-out orientation.