Ovarian hormones and resting potential of rabbit uterine smooth muscle

¹ Department of Pharmacology, State University of New York, Downstate Medical Center, Brooklyn, New York

Myometrial strips isolated from uterus of rabbits under either estrogen or progesterone domination were impaled with glass capillary microelectrodes for measurement of resting potential. This was found to be 49.81 ± 0.34 mv for estrogen-dominated myometrium (mean ±se of 616 samples), and 48.86 ± 0.43 mv for progesterone-dominated myometrium (514 samples), the difference between the resting potentials being insignificant. Therefore, the validity of the so-called "progesterone-block" hypothesis is questioned. Collagen was present in 14 g/kg of wet tissue in both hormonal states. These amounts did not hold sufficient chloride to appreciably lower the intracellular chloride concentrations, which were high enough to suggest either a complex distribution pattern or some active uptake for chloride. The relative cation permeabilities (Pna/Pk) were estimated as 0.11 for the estrogen-dominated myometrium, and 0.17 for the progesterone-dominated myometrium.

Key Words: resting potential of uterine muscle

Submitted on March 2, 1964