HUMAN UTERINE FLUlD POTASSIUM AND THE MENSTRUAL CYCLE

Abstract

Summary Human uterine fluid was obtained from women at laparotomy by a new technique which avoids contamination by cervical and tuba1 fluids. The potassium (K+) concentration of the uterine fluid rose from 17.9 mEq./l. in the follicular phase to 33.7 mEq./l. in the luteal phase (p<0.00l). However, there was a decreased uterine fluid volume in the luteal phase and the total potassium content of the fluid was not increased, suggesting reabsorption of sodium and water rather than the secretion of more potassium. The high uterine fluid K+ concentration, which may reach 39 mEq./l. in the mid‐luteal phase, presumably provides a suitable medium for the blastocyst; there are also reasons for believing that the high K+ concentration of the luminal fluid will reduce the membrane potential of the endometrium, that this will facilitate blastocyst‐endometrial contact and may be essential for blastocyst‐endometrial adhesion.