Electrolytes in vaginal fluid during the menstrual cycle of coitally active and inactive women

Abstract

Vaginal fluid was collected on tampons self-inserted for 4 h daily during the menstrual cycles of coitally active, coitally inactive, ovulatory and non-ovulatory women. The daily hourly rate of fluid collected and its concentrations of Na+, K+, Cl- and Ca2+ were assessed. The fluid revealed a characteristic composition throughout all the menstrual cycles of high K-low Na concentrations compared to plasma, but no characteristic changes occurred with the stage of the cycle. Occasional transient increases and decreases in Na+ and Cl- concentrations were observed, usually closely correlated with one another. Transient changes in K+ occurred but were not always correlated with other ions. In 9 cycles from 7 subjects, the mean .+-. s.e.m. [standard error of the mean] levels (in mmol/kg fluid) of Na+ (82 .+-. 4), K+ (30 .+-. 2) and Cl- (79 .+-. 4) in the first 7 days of the cycles were not significantly different from the Na+ (75 .+-. 5), K+ (30 .+-. 2) and Cl- (72 .+-. 7) concentrations of the last 7 days of the cycles. Apparently differences in hormonal balance between the 2 phases of the menstrual cycle do not influence the ionic levels of vaginal fluid. The concentration of Ca2+ in 3 ovulating subjects varied between 1-5 mmol/kg fluid and appeared to be inversely correlated with the amount of fluid collected.