ANISOMYCIN AND VERAPAMIL INFLUENCE THE ACTION OF PROGESTERONE ON REGULATION OF TERM HUMAN MYOMETRIAL CONTRACTILE ACTIVITY

OBJECTIVE Progesterone has been shown to have both stimulatory and inh ibitory effects on term human myometrial contractile activity. The mec hanisms involved in this action of progesterone are still poorly under stood. DESIGN Myometrial tissues were obtained from the lower uterine segment at elective Caesarean section of 30 term pregnant women. The c ontractile activity of muscle strips was measured by a superfusion tec hnique and protein synthesis evaluated by [H-3]-leucine incorporation. RESULTS [3H]-leucine incorporation into term myometrial strips was no t affected by progesterone (10 mu mol/l), but was markedly reduced by the protein synthesis inhibitor anisomycin (P < 0.05). However, proges terone increased frequency and tonus of contractions and reduced the a ctivity-area of contractions (P < 0.01). Anisomycin (100 mu mol/l) did not change these effects or the spontaneous contractile activity. Rem oval or extracellular Ca2+ or addition of the L-type calcium channel b locker verapamil prevented the spontaneous as well as the progesterone -induced contractions, but had less pronounced effects on contractions initiated by oxytocin. CONCLUSION The results indicate that the actio ns of progesterone on term myometrial contractile activity occur witho ut protein synthesis and that increased Ca2+ influx or decreased outwa rd transport of Ca2+ may play a possible role.