Regional differences in vascular responses in the human uterus

Tissue specimens from the fundus, isthmus and distal cervix were obtained from 14 women at hysterectomy at various phases of the menstrual cycle. Ring preparations of small intramyometrial and intracervical arteries were dissected and mounted in organ baths; isometric tension was recorded and responses to contractile agents were studied. The amplitude of responses to K+ (124 mmol/l) of the vessel preparations ranked fundus greater than or equal to isthmus greater than cervix. While similar pD2 values for noradrenaline (NA) were found, the Emax values ranked cervix greater than or equal to isthmus greater than or equal to fundus (cervix greater than fundus). The pD2 values for arginine-vasopressin (AVP) showed minor differences, while the Emax values for this peptide ranked fundus greater than or equal to isthmus greater than or equal to cervix (fundus greater than cervix). Arteries from the fundus and isthmus displayed weak, inconsistent contractile responses to prostaglandin F2 alpha, but more pronounced contractions were induced by this prostanoid in arterial preparations from the distal cervix. The results suggest regional differences in vascular mechanical responses to endogenous vasoactive agents in the human uterus.