Operational correlates of prostanoid TP receptor expression in human non-pregnant myometrium are unaffected by excision site or menstrual cycle status of the donor.

1. Cumulative concentration-effect curves for the selective prostanoid TP receptor agonist, U46619, were constructed in strips of human non-pregnant myometrium grouped according to tissue excision site (top, lateral wall, lower uterine segment, sub-serosal or sub-endometrial), tissue orientation (strips cut either parallel or perpendicular to the serosa) and donor menstrual status (proliferative or secretory phase). 2. U46619 was excitatory in all tissues. There was no significant difference in either pEC50 or maximum response between groups (P<0.05). The range of pEC50 values was 6.8+/-0.1 (lateral wall, proliferative phase, n=5) to 7.1+/-0.3 (lateral wall, secretory phase, n=5). The range of maximum response values was 0.9+/-0.8 N cm-2 (lateral wall, proliferative phase, n=5) to 3.1+/-1.0 N cm-2 (lateral wall, secretory phase, n=5). 3. Saturation binding analyses were conducted using the radiolabelled TP receptor agonist, [125I]-BOP. Binding parameters were estimated for membranes prepared from human non-pregnant myometrium excised from the lateral wall and grouped according to donor menstrual status. 4. There were no significant differences in the mean pKd and [R]tot values for [125I]-BOP binding between the two groups (proliferative phase: pKd=8.3+/-0.3, [R]tot=412+/-319 fmol mg protein-1, n=5; secretory phase: pKd=8.5+/-0.4, [R]tot=369+/-192 fmol mg protein-1, n=6; P<0.05). 5. These data indicate that U46619-mediated responses in human non-pregnant myometrium are not influenced by tissue excision site, tissue orientation or donor menstrual status and that [125I]-BOP binding is not influenced by donor menstrual status. This suggests that the TP receptor population is homogeneous throughout the human non-pregnant myometrium, and not subject to hormonal regulation.