Effects of progesterone and oxytocin on intracellular elemental composition of term human myometrium in vitro.

OBJECTIVE

To study the effects of progesterone and oxytocin on contractile activity related to the intracellular elemental composition of human pregnant myometrium.

STUDY DESIGN

Myometrial strips were mounted in tissue baths and superfused with plain buffer, oxytocin or progesterone. Progesterone was initially added to the tissue bath or at the onset of spontaneous contraction of the strips. The myometrial contractile activities were recorded isometrically and the results were analyzed by a specific computer program. The effects of oxytocin and progesterone on the intracellular elemental composition were studied by X-ray microanalysis in an electron microscope.

RESULTS

The contractile activity in terms of frequency and tonus of the muscle strips was increased by oxytocin and progesterone. This increase was more pronounced if progesterone was added to the bath at the start of the experiment. After 120 min of incubation with oxytocin and progesterone the total intracellular concentration of calcium was significantly higher (P < 0.0001 and P < 0.002, respectively) compared to buffer.

CONCLUSIONS

(i) Oxytocin increases total intracellular calcium concentration concomitant with an increase in uterine contractile activity. (ii) Progesterone increases the myometrial tone and frequency of contractions, simultaneously with an increase in total intracellular calcium.