AJP - Heart and Circulatory Physiology, Vol 244, Issue 3 335-H340, Copyright © 1983 by American Physiological Society
Increased sensitivity to angiotensin in uterine arteries from pregnant rabbits
D. M. Moisey and T. Tulenko
This study was designed to compare the vascular reactivity intrinsic to
uterine and femoral arterial smooth muscle from pregnant (0.92 term) and
nonpregnant rabbits to angiotensin II (ANG II), norepinephrine (NE), and
potassium chloride (KCl) using the isolated helical strip technique.
Comparing dose-response relations, arteries from both groups were equally
sensitive to NE and KCl. Uterine arteries from pregnant rabbits, however,
exhibited a greater sensitivity to the vasoconstricting effects of ANG II
(P less than 0.01). This selective increase in sensitivity to ANG II was
not observed in femoral arteries. The altered ANG II response in uterine
arteries from pregnant rabbits was unaffected by pretreatment with cocaine
or phenoxybenzamine, thus ruling out an adrenergic mechanism mediating the
response. In addition, evaluation of saralasin affinity (KB) for the
uterine arterial ANG II receptor suggested that it was not altered in
pregnancy. However, preincubation of uterine arteries from pregnant rabbits
with meclofenamate or indomethacin consistently attenuated the ANG II
response (P less than 0.05). Therefore, this study demonstrated that 1)
uterine arteries from term pregnant rabbits show a selective and specific
enhancement to ANG II vasoconstriction, and 2) this increased response of
ANG II results from the local ANG II stimulation of synthesis of
prostaglandins by the uterine arterial wall that have a net
vasoconstricting action.
