[Physiologic variability of erythrocyte concentrations and transport of sodium and potassium].

Sodium concentrations in erythrocytes are lower in women during the luteal phase of the menstrual cycle than in women studied during the follicular phase and in men. Sodium cotransport activity is lower in women during the follicular phase than in men. Women taking oral contraceptives show no monthly variations in erythrocyte sodium concentrations.

Intra-erythrocyte concentration and transmembrane fluxes of sodium and potassium during acute and short-term administration of ketanserin in normal male subjects.

The effect of acute and short-term administration of ketanserin on the intracellular concentration and transmembrane fluxes of sodium and potassium in erythrocytes was studied in 12 sodium-replete, normal male subjects. The subjects received 40 mg ketanserin three times a day for one week. Blood samples were drawn before and 2.

In vitro inhibition of renal sodium-potassium ATPase activity by progesterone.

The effect of various steroids and prostaglandins on the activity of canine kidney Na+, K+-ATPase activity was tested in vitro. Progesterone induced a dose-dependent increase in inhibition of the canine kidney Na+, K+-ATPase activity. Aldosterone, cortisol, cortisone as well as prostaglandin E2 and 13,14-dihydro-15-keto-prostaglandin F2 alpha, did not cause an inhibition of canine kidney Na+, K+-ATPase.

Assessment of sodium-potassium ATPase activity in human erythrocytes in vitro.

The red cell Na+,K+-ATPase pump activity was measured either by the ouabain-sensitive 86Rb-uptake in the presence or absence of 4 mM potassium in the external medium or by the ouabain-sensitive Na+-efflux in normal male subjects without any medication (n = 14) and during short-term treatment with the serotonin-antagonist, ketanserin. The ouabain-sensitive 86Rb-uptake in a medium containing 4 mM K+ was related to the 86Rb-uptake in a K+-free medium (r = 0.82; p less than 0.