• S Maigaard, A Forman, and K E Andersson.
• Acta Physiol. Scand. 1986 Sep 1; 128 (1): 23-31.

AbstractTissue specimens from various parts of the uteroplacental unit were obtained from women undergoing caesarean section, and placental tissue from women with normal deliveries. Strips of myometrial tissue, and segments of intramyometrial arteries were dissected together with segments of chorionic plate arteries and veins, and stem villous arteries. The preparations were mounted in organ baths, isometric tension recorded, and the responses to angiotensin II, vasopressin, and oxytocin were studied. In myometrial preparations, angiotensin caused a slight, transient increase in the frequency of spontaneous contractions, but no changes in amplitude. In all vascular preparations angiotensin produced concentration-related contractions. The responsiveness of the preparations was myometrial artery greater than villous artery greater than chorionic plate artery = chorionic plate vein. All responses were transient and tachyphylaxis was pronounced in all tissues. Tachyphylaxis was not influenced by pretreatment with indomethacin. Vasopressin increased transiently frequency and amplitude of contractions in myometrial strips. Myometrial arteries responded with a sustained contraction, as did chorionic plate arteries and veins but the latter vessels were less responsive. Villous arteries did not respond to vasopressin. Oxytocin preferentially stimulated myometrial strips, but also had a weak concentration-related contractant effect on chorionic plate arteries and veins. Villous arteries did not respond to oxytocin. At a higher concentration, causing a pronounced increase in the frequency and amplitude of contractions of myometrial strips, oxytocin abruptly caused a marked contraction of myometrial arteries. Lower concentrations of the peptide had almost no effects. The results suggest that various smooth muscle tissues of the human uterus and placenta are highly differentiated as regards responses to angiotensin II, vasopressin, and oxytocin. The physiological and possible clinical importance of the present findings deserve further investigation.

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