Oxytocin Receptors in the Porcine Myometrium during the Estrous Cycle and Early Pregnancy

Affinity (Kd) of oxytocin receptors (OTR) in the porcine myometrium ranged from 0.48 to 0.77nM. There was not significant difference in Kd values among the stages of the estrous cycle and early pregnancy. However, maximum number of OT binding site varied with the stages of the estrous cycle, but were constant at early pregnancy. These results suggested that OT in the myometrium probably plays a role for uterine contraction via OTR in the estrous stages instead of controlling the luteal function.