TY - JOUR
T1 - Angiotensin II indirectly vasoconstricts the ovine uterine circulation
AU - Cox, Blair E.
AU - Williams, Carrie E.
AU - Rosenfeld, Charles R.
PY - 2000/2
Y1 - 2000/2
N2 - The uterine vasculature of women and sheep predominantly expresses type 2 ANG II receptors that do not mediate vasoconstriction. Although systemic ANG II infusions increase uterine vascular resistance (UVR), this could reflect indirect mechanisms. Thus we compared systemic and local intra- arterial ANG II infusions in six near-term pregnant and five ovariectomized nonpregnant ewes to determine how ANG II increases UVR. Systemic ANG II dose- dependently (P > 0.001) increased arterial pressure (MAP) and UVR and decreased uterine blood flow (UBF) in pregnant and nonpregnant ewes; however, nonpregnant responses exceeded pregnant (P < 0.001). In contrast, local ANG II infusions at rates designed to achieve concentrations in the uterine circulation comparable to those seen during systemic infusions did not significantly decrease UBF in either group, and changes in MAP and UVR were absent or markedly attenuated. When MAP rose during local ANG II, which only occurred with doses ≥2 ng/ml, increases in MAP were delayed more than twofold compared with responses during systemic ANG II infusions and always preceded decreases in UBF, resembling that observed during systemic ANG II infusions. These observations demonstrate attenuated uterine vascular responses to systemic ANG II during pregnancy and suggest that systemic ANG II may increase UVR through release of another potent vasoconstrictor(s) into the systemic circulation.
AB - The uterine vasculature of women and sheep predominantly expresses type 2 ANG II receptors that do not mediate vasoconstriction. Although systemic ANG II infusions increase uterine vascular resistance (UVR), this could reflect indirect mechanisms. Thus we compared systemic and local intra- arterial ANG II infusions in six near-term pregnant and five ovariectomized nonpregnant ewes to determine how ANG II increases UVR. Systemic ANG II dose- dependently (P > 0.001) increased arterial pressure (MAP) and UVR and decreased uterine blood flow (UBF) in pregnant and nonpregnant ewes; however, nonpregnant responses exceeded pregnant (P < 0.001). In contrast, local ANG II infusions at rates designed to achieve concentrations in the uterine circulation comparable to those seen during systemic infusions did not significantly decrease UBF in either group, and changes in MAP and UVR were absent or markedly attenuated. When MAP rose during local ANG II, which only occurred with doses ≥2 ng/ml, increases in MAP were delayed more than twofold compared with responses during systemic ANG II infusions and always preceded decreases in UBF, resembling that observed during systemic ANG II infusions. These observations demonstrate attenuated uterine vascular responses to systemic ANG II during pregnancy and suggest that systemic ANG II may increase UVR through release of another potent vasoconstrictor(s) into the systemic circulation.
KW - Angiotensin receptors
KW - Nonpregnant
KW - Pregnancy
KW - Uterine blood flow
KW - Uteroplacental circulation
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U2 - 10.1152/ajpregu.2000.278.2.r337
DO - 10.1152/ajpregu.2000.278.2.r337
M3 - Article
C2 - 10666133
AN - SCOPUS:0034016120
SN - 0363-6119
VL - 278
SP - R337-R344
JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology
IS - 2 47-2
ER -