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 KD and BMax. 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 KD and BMax, in females this is not present. However, in females there is a significantly lower KD 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.