Torbjörn Bäckström

Influence of route of administration on progesterone metabolism

While inducing similar progesterone levels, the ratio of 5 alpha- and 5 beta-pregnanolone/progesterone plasma concentrations has been dramatically increased after oral as opposed to vaginal administration, in a cross-over study. The known psychotropic effects of 5 alpha- and 5 beta-pregnanolone lead to different indications and precautions for oral and vaginal administration of progesterone.

Sex steroid receptors and human parturition

Objective To investigate the correlation between sex steroid hormones and their receptors during normal and dysfunctional labor. Methods Myometrial and decidual biopsies along with maternal and cord blood samples were taken from women with or without labor activity. Estrogen and progesterone receptor contents in myometrum and decidua were determined by enzyme immunoassay, and hormone concentrations were analyzed by radioimmunoassay. Results In the lowere segment of the uterus, the prosgesterone receptor concentrations of myometrum were significantly lower in oxytocin-resistant dystocia compared with those of normal labor and before labor (P < .04, P < .005. respectively). No significant difference was found in the estrogen receptors of myometrum from the upper segment showed higher concentrations in active labor compared with those before labor and oxytocin-resistant labor (P < .01, P < .05, respectively). Estrogen receptors from the upper segment showed no significant difference in these regards. The was no difference in peripheral and myometrial sex hormone levels in the groups studied. Conclusion These data suggest that, in the human, 1) oxytocin-resistant labor is associated with low levels of progesterone receptors, 2) estrogen receptors, 2) estrogen receptors content in myometrium might have no or little relation to labor, and 3) functional labor seems not to be related to a decreased progesterone activity in the myometrium.

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.

Morphometric analysis of gap junction density in human myometrium at term

In the human myometrium. the formation of gap junctions in the various stages of labor and, in correlation with the concentration of progesterone in the maternal blood, has not been described adequately. The accepted hypothesis that raised concentrations of progesterone in maternal blood in animals prevent the formation of gap junctions was scrutinized in human niyometrium. Myometrial tissue was examined by electron microscopy for the presence of gap lunctions and analyzed morphometrically in 17 women who had an elective or emergency cesarean operation at the 38th or 39th week of pregnancy. The concentrations of progesterone and estradiol in the maternal and cord blood was measured by means of radioimiiiunoassay. The frequency and area of gap junctions varied in relation to the presence or absence of labor. In the myometrium of women in labor, gap junctions were most frequent (5.2/1000 μm of cell membrane), their area largest (0.32 μ2/1000 μm of cell membrane) and their fractional area greatest (0.20%). When the women were not in genuine labor or when contractions were weak, the percentage fractional areas of gap junctions were low (0.020‐0 090) and the gap junctions very small. In the pre‐ and active phases of labor, the concentration of progesterone in maternal blood was significantly higher (p <0.025 and 0.03 respectively) than in women who were not in labor.