Age-related determination of the basal and calmodulin-stimulated human RBC Ca2+-ATPase activity

Abstract

The basal and calmodulin-stimulated activity of the human erythrocyte Ca2(+)-ATPase was determined in 56 healthy individuals of different ages in order to set control values. The basal activity of all 56 healthy subjects was 0.805 +/- 0.525 mumole hydrolyzed ATP/mg protein/hr, while the calmodulin-stimulated activity gave an average of 2.437 +/- 0.785 mumole hydrolyzed ATP/mg protein/hr. There was no significant difference in basal Ca2(+)-ATPase activity in males and females; however, significantly increased levels of the stimulated red cell calcium pump was seen in females. Based on age, the basal activity for newborns and children up the age of 7 years was higher than that for adults and a distinct increase in activation by calmodulin was observed with a maximum at the age range of 8-13 years. It was demonstrated that for the investigation of Ca2(+)-ATPase activities in children different normal values must be taken into consideration than for those already reported for adults. Our data may serve as controls for Ca2(+)-ATPase activities for comparison purposes and for further studies from different diseases in childhood where increased intraerythrocytic calcium levels are reported.