Effect of Calcium-Binding Protein on Adenosine 5'-Triphosphatase Activity in the Brain Cytosol of Rats of Different Ages : The Inhibitory Role of Regucalcin

抄録

Adenosine 5'-triphosphatase (ATPase) plays a role in the process of energy conversion in the controlled hydrolysis of ATP. The effect of Ca²⁺ -binding protein on ATPase activity in the brain cytosol of rats of different ages was investigated. ATPase activity in the brain cytosol of 50-week-old rats was significantly decreased as compared with that of 5-week-old rats. The presence of calcium chloride (10^-5 and 10^-4 M) in the enzyme reaction mixture caused a significant increase in ATPase activity in the brain cytosol of rats of different ages. This incrase was not altered by trifluoperazine (2×10^-5 M), an antagonist of calmodulin. Calmodulin (5 μg/ml), calbindin (5 μg/ml) or S-100A protein (10 μg/ml), a Ca²⁺ -binding protein, had no effect on ATPase activity. Meanwhile, regucalcin (10^-9 M), which is present in brain, significantly decreased ATPase activity in young and older rats. However, the effect of regucalcin was weakened by the presence of Ca²⁺ (10^-5 M). The addition of anti-regucalcin monoclonal antibody in the reaction mixture caused a significant elevation of ATPase activity; this increase was completely abolished by adition of regucalcin (10^-9 M). The present study suggests that regucalcin plays an inhibitory role in the regulation of ATPase activity in the brain cytosol of rats of different ages.