SEX DIFFERENCES IN HUMAN LYMPHOCYTE Na,K-ATPase AS STUDIED BY LABELED OUABAIN BINDING

Abstract

Lymphocytes Na,K-ATPase is a plasma membrane enzyme that is up-regulated under lymphocytes activation. It is also studied as a model of brain cells Na,K-ATPase. Data about sex-related specificities of the enzyme are not available.The binding of tritium-labelled ouabain to lymphocyte plasma membrane Na,K-ATPase was studied in healthy volunteers of both sexes. The binding interactions were expressed in terms of K_D and B_Max. The first parameter is related to the affinity of ouabain for the enzyme whereas the second one is related to its density on the cell membrane. Distinct sex-related differences were found. Whereas in males there is a significant direct correlation between the parameters K_D and B_Max, in females this is not present. However, in females there is a significantly lower K_D in the 25–37 age range. The latter result probably reflects the expression of subunit variants giving a greater affinity for ouabain. This circumstance may be relevant both to lymphocytes’ ability to be activated and to brain function, if one admits that lymphocyte Na,K-ATPase faithfully represents the brain-borne one.

Keywords:

• blood
• lymphocytes
• Na,K-ATPase
• ouabain binding
• sex differences