Preparation and characterization of rabbit myometrial cells in primary culture: influence of estradiol and progesterone treatment.

Myometrial cells were obtained following a three-step enzymatic digestion of uterine horns from Day 1 pseudopregnant rabbits. Isolated cells were cultured in RPMI 1640 supplemented with 10% fetal bovine serum (FBS), whole or steroid depleted (FBS-DC) at a plating density of 0.5 X 10(6) cells/ml. The cells reached confluency on Day 6 to 7 with whole serum and on Day 7 to 8 with DC serum. The process yielded myometrial cells at a purity level of at least 80% as assessed by indirect immunofluorescence using desmin antibody on confluent cultures. The addition of increasing doses of 17 beta-estradiol (E2) (0.1 nM to 1 microM) to the culture medium resulted in an increase in total protein and DNA content (1.5-fold at 1 nM). Similar treatment with progesterone (P) resulted in a 25% inhibition of protein and DNA content at 10 nM. Pretreatment of cells with E2 (1 nM) for 3 d followed by P (10 nM) for 3 d resulted in a 1.8-fold stimulation of protein with a higher protein: DNA ratio indicating that the increase was due to cellular hypertrophy. Analysis of desmin by polyacrylamide gel electrophoresis showed that this cytoskeleton protein was not affected by steroid treatment. Our results indicate that PR can generate two different responses depending on cell pretreatment. In as much as myometrial cells grown in primary culture respond differentially to E2 and P they should provide a useful model to study the regulation of myometrial contractility.