Adaptation to pregnancy leads to attenuated rat uterine artery smooth muscle sensitivity to oxytocin.
OBJECTIVE
We tested the hypothesis that oxytocin (OT) contracts blood vessels via vasopressin V1A (VP) receptors, and that this depends on pregnancy.


METHODS
Concentration-contraction relationships (CCR) to OT and VP (10(-12)-10(-6) mol/L) were obtained in different blood vessels. CCR were obtained in uterine arteries (UA) from nonpregnant, mid-pregnant, and late pregnant rats (n = 6-10 per group) in the absence and presence of selective antagonists (10(-7) mol/L).


RESULTS
Sensitivity to OT, but not to VP, is attenuated in pregnant rat UA. Antagonists shifted CCR of OT and VP to the right, and, to a lesser extent, of the counterpart, in all UA. VP antagonist depresses oxytocin CCR much more than OT antagonist in pregnant rat UA.


CONCLUSIONS
OT and VP contract UA via their own receptors, although partial cross-activation is evident. Adaptation to pregnancy led to attenuated sensitivity of UA smooth muscle to OT and transformed OT receptors into VP-like ones.
Vedernikov
Yuri P
YP
Division of Reproductive Sciences, Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, TX, USA.
Betancourt
Ancizar
A
Wentz
Melissa J
MJ
Saade
George R
GR
Garfield
Robert E
RE
D000222:Adaptation, Physiological; D000818:Animals; D065092:Antidiuretic Hormone Receptor Antagonists; D001013:Aorta, Thoracic / Q000187:drug effects; D001127:Arginine Vasopressin / Q000031:analogs & derivatives / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D003199:Computer Systems; D004305:Dose-Response Relationship, Drug; D005260:Female; D005263:Femoral Artery / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009994:Osmolar Concentration; D010120:Oxytocics / Q000008:administration & dosage / Q000494:pharmacology*; D010121:Oxytocin / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D011247:Pregnancy; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018045:Receptors, Oxytocin / Q000037:antagonists & inhibitors / Q000235:genetics; D017483:Receptors, Vasopressin / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014599:Uterus / Q000098:blood supply*; D014661:Vasoconstriction; D014667:Vasopressins / Q000008:administration & dosage / Q000037:antagonists & inhibitors / Q000494:pharmacology
D065092:Antidiuretic Hormone Receptor Antagonists; D010120:Oxytocics; D012333:RNA, Messenger; D018045:Receptors, Oxytocin; D017483:Receptors, Vasopressin; C509322:oxytocin, d(CH2)5(1)-Tyr(OMe)(2)-Orn(8)-; C509323:vasopressin, d(CH2)5(1)-Tyr(OMe)(2)-Arg(8)-; D014667:Vasopressins; D001127:Arginine Vasopressin; D010121:Oxytocin