AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 4 889-R894, Copyright © 1990 by American Physiological Society

ARTICLES

Transuterine ion movement and electrical potential difference in pregnant guinea pigs

P. S. Dale, T. G. McNaughton, L. A. Power, R. D. Gilbert and G. G. Power
Department of Physiology, Loma Linda University, School of Medicine, California 92350.

An investigation of the site and mechanism responsible for the maternal-fetal electrical potential difference (PD) was done in 11 anesthetized guinea pigs at 54-56 days gestation. We removed the most distal fetus and placenta from one uterine horn and secured a catheter, thermistor, and Ag-AgCl electrode in the resulting pouch. The pouch was filled with Earle's solution. We placed another thermistor and electrode in the maternal abdomen. The PD between electrodes was monitored continuously; periodic samples of maternal blood and intrauterine fluid were taken. Thirty minutes after the uterus was filled, the PD (uterine cavity negative) averaged 29.6 +/- 4.5 (95% confidence interval of the mean) mV. Over 4 h, intrauterine K+ concentration [( K+]) decreased from 4.9 to 2.6 +/- 0.5 meq/l, against a chemical and electrical gradient. In eight animals, we measured bidirectional Na+ flux using 22Na and 24Na. The flux ratio was not distinguishable from unity despite a significant PD. Our data indicate that the maternal-fetal PD is probably generated by the endometrial epithelium and that Na+ and K+ both move across the epithelium by active transport or cotransport rather than simple diffusion.

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				S. Ward, E. Jauniaux, C. Shannon, C. Rodeck, R. Boyd, and C. Sibley Electrical potential difference between exocelomic fluid and maternal blood in early pregnancy Am J Physiol Regulatory Integrative Comp Physiol, May 1, 1998; 274(5): R1492 - R1495. [Abstract] [Full Text] [PDF]