Changes in sodium transport during the human menstrual cycle and pregnancy.
1. We have studied the transport of Na+ and K+ by erythrocytes during the follicular and luteal phases of the human menstrual cycle, and in pregnant compared with non-pregnant women. Venous blood was drawn from 10 healthy young women (not taking any medication or hormones) 1-2 days after menstruation and from the same women 7-9 days after ovulation. For the pregnancy part of the study, blood was drawn from eight other normotensive non-pregnant women and from eight age-matched normotensive pregnant women (36-43 weeks gestation). 2. Intracellular erythrocyte and plasma Na+ and K+ concentrations were measured by flame photometry. The increase in the intracellular Na+ concentration during a 1 h 37 degrees C incubation of fresh whole blood with 0.2 mmol/l ouabain (compared with no ouabain) was measured to determine the rate of active Na+ efflux. The Na(+)-K+ pump rate constant was calculated by dividing the active Na+ efflux rate by the intracellular Na+ concentration. 3. In fresh blood, the intracellular erythrocyte Na+ concentration (P < 0.002) and the plasma K+ concentration (P < 0.01) were both lower in pregnant than in non-pregnant women. The Na(+)-K+ pump rate constant was higher (P < 0.02) during the luteal phase than during the follicular phase, and in pregnant compared with non-pregnant women. 4. We conclude that short-acting hormones in the plasma most probably account for the changes in the Na(+)-K+ pump rate constant during the menstrual cycle.
Webb
G D
GD
Department of Physiology and Biophysics, University of Vermont College of Medicine, Burlington.
Ashmead
G G
GG
al-Mahdi
S
S
Auletta
F J
FJ
McLaughlin
M K
MK
D000328:Adult; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D005498:Follicular Phase / Q000378:metabolism; D006801:Humans; D008183:Luteal Phase / Q000378:metabolism; D008598:Menstruation / Q000378:metabolism*; D010783:Photometry; D011247:Pregnancy / Q000378:metabolism*; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase