A PILOT-STUDY OF ERYTHROCYTE LITHIUM-SODIUM COUNTERTRANSPORT IN WOMENDURING THE MENSTRUAL-CYCLE

Objective: The study investigated lithium-sodium countertransport in e rythrocytes of normal female volunteers during different phases of the menstrual cycle or during administration of oral contraceptives. Meth ods: Ten normally menstruating, and eight oral contraceptive using, no rmal female subjects were studied over at least one cycle. Erythrocyte lithium-sodium countertransport was determined using standard, previo usly validated methods at different phases of the menstrual cycle. Hem atological, electrolyte, blood pressure and other transport measures w ere also made and these were related to the self-reported incidence of premenstrual symptomatology. Results: A correlation, (p < 0.02), was found between lithium-sodium countertransport rate and the premenstrua l symptom severity score but only in the premenstrual phase. There was no correlation between any of the electrolyte, blood pressure or hema tological data and lithium-sodium countertransport rate nor between it and other ion transport measures. Pre-menstrual symptomatology was co nspicuously absent from those subjects taking oral contraceptives. Cyc lical fluctuations in normally menstruating women, and differences bet ween them and oral contraceptive users, were seen in lithium-sodium co untertransport rate although the groups were too small to show statist ical significance. Conclusions: Care was taken to exclude influences d ue to circadian, dietary and diurnal variations and the present result s show somewhat less within-individual variability in erythrocyte lith ium-sodium countertransport during the menstrual cycle than do other r eports in the literature. Some interesting features were observed whic h justify a much larger scale study than the present pilot experiment which should involve a larger number of subjects studied over more tha n one cycle and in particular a more detailed study of the ovulatory p hase.