Erythrocyte cation transport is sex-related and is modified by oral contraceptives.

Cation transport across the erythrocyte membrane was studied in normotensive male and female subjects, 20 to 45 years of age. Inward sodium-potassium cotransport was found to be significantly greater in men than in women who were not taking oral contraceptives. Intracellular potassium concentration was lower in men than in women, and was inversely correlated with cotransport. Women who were using oestrogen-progestogen oral contraceptives had higher cotransport than those who were not. It is concluded that a difference in cotransport exists between Caucasian men and women, which is not evident if women are taking oral contraceptives, and which could invalidate comparisons of cation transport between subject groups that are not sex-matched.