Faculty Bibliography

In an in vitro human myometrial strip system, both relaxin and progesterone can independently decrease the amplitude of spontaneous myometrial contractions. However, progesterone and relaxin synergize in this action. Doses of relaxin and progesterone which independently are ineffective, together inhibit myometrial contraction amplitude. Relaxin and progesterone are both products of the corpus luteum, a structure necessary for early pregnancy maintenance. The synergistic action of relaxin and progesterone in vitro suggests a similar in vivo physiologic effect in establishing uterine quiescence

Serum relaxin concentrations were quantitated throughout pregnancy. Relaxin levels were higher in the first than in either succeeding trimester of pregnancy. Relaxin concentrations in third-trimester twin pregnancies were not significantly different from those in singleton pregnancies. Relaxin levels in toxemic pregnancies were similar to those of normal pregnancy. In contrast, relaxin concentrations in pregnancies beyond 43 weeks' gestation and in women with premature labor were significantly lower than levels in normal women in the third trimester of pregnancy

Relaxin is a peptide hormone secreted by the human corpus luteum of pregnancy . Aqueous extracts of relaxin-rich pregnancy corpora lutea decreased the amplitude of spontaneous human myometrial strip contractions in vitro. Relaxin-poor extracts of menstrual cycle corpora lutea did not affect contractions. Antibody precipitation of relaxin from pregnancy luteal extracts eliminated the effect on myometrial strips. Relaxin removal was confirmed by bioassay. This demonstrates an inhibiting action of human relaxin on human myometrial tissue in vitro. This action suggests a mechanism for maintaining uterine quiesence in early pregnancy.

A 31-year-old woman developed unilateral endometriosis at the site of ovarian implantation to a uterine window. This complication of the Estes procedure resembles the experimental endometriosis induced in rhesus monkeys by causing intraabdominal menstruation. This adds support to the Sampson hypothesis of endometriosis development.