In order to investigate the osmolar effect on the moitlity of nonpregnant uterus, intrauterine rpressures was recorded, infusing isotonic or hypertonic saline into the uterine cavity of adult female rabbits. In another series of experiment, the longitudinal tension of isolated uterine muscle strip was recorded. The concentration of sodium chloride in the bathing solution . was increased in orderly sequence.
The animals were divided into three groups. They were; Group 1. Seven rabbits of control.
Group 2. Nine rabbits administered 25 ug/kg of estrogen daily, for seven days. Group 3. Seven rabbits injected 0. 5mg/kg of progesterone daily, for five days following estrogen administration of seven days.
The intrauterine pressure generated by contraction of the uterine musculature was transmitted to pressure transducer via liquid column in polyethylene tubing inserted in the uterine cavity, and was recoredd on a physiograph.
The longitudinal tension of isolated uterine muscle strip was recorded on the physiograph by way offorce transducer through cotton thread.
The area beneath the pressure curve or the tension curve in the recording paper represented. the magnitude of the pressure impulse or the tension impulse, respectively, in a finite period. The frequency of uterine contraction was obstained by countingg the number of waves in five´ minutes period, and the tonus of the uterine smooth muscl was evaluated´ by measuring the upward shift of baseline in each phase.
The results obtained were as follows:
1) Uterine motility increased within 30 minutes of intrauterine infusion of hypertonic saline, and further increase was observed in 1 hour.
2) Plasma osmolarity and sodium concentration increased in accordance with the intrauterine infusion of hypertonic saline solution. The average differences were more than 12 mOsm/L and 6 mEq/L respectively, in 1 hour.
3) Uterine motility in vitro generally increased in proprtion to the sodium chloride concentration of the eternal solution upto 1. 5% of sodium chloride concentration. Specifically, however, the impules of tension decreased gradually above that point, making a peak at 1.5%W
4) It was suggested that hypertonic saline solution might stimulate the uterine smooth muscle, presumablly by electrotonic mechanism including an alteration in sodium-potassium exchange diffusion.
5) Estrogen and progesterone seemed not to bear any significant explicit relationship with the osmolar effect on uterine motility.
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