17-hydroxyprogesterone caproate reverses induced vasoconstriction of the fetoplacental arteries by the thromboxane mimetic U46619

Objective: This study was undertaken to determine whether 17-hydroxyprogesterone caproate (17P) has a vasoactive effect on fetoplacental vasculature. Study design: Two cotyledons were obtained from each of 5 placentas. Baseline perfusion was established with Hanks-based solution. One cotyledon from each pair was then infused with perfusate to which U46619 a thromboxane sympathomimetic had been added. After 30 minutes, a dose of 17P was then administered to each cotyledon. Finally, a vasoconstricting dose of angiotensin II was administered to each cotyledon. Perfusion pressures were recorded throughout. Statistical analysis of pressure change for a single cotyledon was performed by using a paired t test. Statistical analysis of mean perfusion pressure difference between U46619 exposed and nonexposed cotyledons was analyzed by using a students t test. Results: 17P did not significantly alter the perfusion pressure of the control cotyledon. (30.6 ± 8.3 mm Hg vs 30.1 ± 7.8 mm Hg P = .48). 17P administration significantly lowered the perfusion pressure of the U46619 preconstricted vessels in comparison with preadministration. (60.1 ± 13 mm Hg vs 27.3 ± 7.1 mm Hg P = .03). Both groups of cotyledons responded with vasoconstriction to angiotension II with no difference in response between groups (38.3 ± 12 mm Hg vs 45.8 ± 8.2 mm Hg P = .63). Conclusion: 17P reverses induced vasoconstriction by U46619 in fetoplacental arteries.