FE2-INDUCED INHIBITION OF GERBIL FOREBRAIN MICROSOMAL CA2+-ATPASE - EFFECT OF STOBADINE, GLUTATHIONE AND COMBINATION OF BOTH ANTIOXIDANTS()

The incubation of the gerbil forebrain microsomes in the presence of f errous sulphate and EDTA for either 30 min or for 60 min at a temperat ure of 37 degrees C led to the inhibition of Ca2+-ATPase in both a con centration-and time-dependent manner. The concentrations of Fe2+ which led to the inhibition of 50% of the Ca2+-ATPase activity (IC50-value) at these times were 0.59 mM and 0.07 mM, respectively. The preincubat ion of microsomes with 0.1 mM of stobadine prevented the inhibition of Ca2+-ATPase, however, the effectivity of prevention was dependent on the Fe2+ concentration. The net effect of stobadine was an increase in IC50-value to 0.76 mM. Unlike stobadine, reduced glutathione is a nat urally occurring water soluble antioxidant. Glutathione at the concent ration of 0.1mM had no significant protective effect on the inhibition of Ca2+-ATPase. The protective effect of a stobadine-glutathione mixt ure was also investigated; 0.1mM of stobadine in combination with 0.1m M of glutathione was more potent in prevention of Fe2+-induced inhibit ion of Ca2+-ATPase than stobadine alone (IC50 = 1.31 mM). In addition, we have investigated the effect of various stobadine-glutathione mola r ratios (the total concentration of both antioxidants being 0.2mM) on Fe2+-induced inhibition of Ca2+-ATPase. The results indicated that th e best stobadine-glutathione ratio was close to 1 : 1. The effect of 0 .04 mM stobadine in combination with 0.16 mM glutathione was comparabl e to the effect of 0.2 mM of stobadine alone, whereas 0.2 mM glutathio ne was almost ineffective. These results may suggest a possible role o f membrane in Fe2+-induced inhibition of Ca?+-ATPase. (C) 1998 Elsevie r Science B.V.